ActiveState!

ActivePerl Documentation
Table of Contents

(Usage Statistics)
(about this ver)


* Getting Started
    * Welcome To ActivePerl
    * Release Notes
    * Readme
    * ActivePerl Change Log
* Install Notes
    * Linux
    * Solaris
    * Windows
* ActivePerl Components
    * Overview
    * PPM
    * Windows Specifics
       * OLE Browser
       * PerlScript
       * Perl for ISAPI
       * PerlEZ
* ActivePerl FAQ
    * Introduction
    * Availability & Install
    * Using PPM
    * Docs & Support
    * Windows Specifics
       * Perl for ISAPI
       * Windows 9X/NT/2000
       * Quirks
       * Web Server Config
       * Web programming
       * Programming
       * Modules & Samples
       * Embedding & Extending
       * Using OLE with Perl
* Windows Scripting
    * Active Server Pages
    * Windows Script Host
    * Windows Script Components

Core Perl Documentation


* perl
* perlfaq
* perltoc
* perlbook

* perlsyn
* perldata
* perlop
* perlreftut
* perldsc
* perllol

* perllexwarn
* perldebug

* perlrun
* perlfunc
* perlopentut
* perlvar
* perlsub
* perlmod
* perlpod

* perlstyle
* perlmodlib
* perlmodinstall
* perltrap
* perlport
* perlsec

* perlref
* perlre
* perlform
* perllocale
* perlunicode

* perlboot
* perltoot
* perltootc
* perlobj
* perlbot
* perltie

* perlipc
* perlnumber
* perlfork
* perlthrtut

* perldiag
* perlfaq1
* perlfaq2
* perlfaq3
* perlfaq4
* perlfaq5
* perlfaq6
* perlfaq7
* perlfaq8
* perlfaq9

* perlcompile

* perlembed
* perlxstut
* perlxs
* perlguts
* perlcall
* perlfilter
* perldbmfilter
* perlapi
* perlintern
* perlapio
* perltodo
* perlhack

* perlhist
* perldelta
* perl5005delta
* perl5004delta

* perlamiga
* perlcygwin
* perldos
* perlhpux
* perlmachten
* perlos2
* perlos390
* perlvms
* perlwin32

Pragmas


* attributes
* attrs
* autouse
* base
* blib
* bytes
* charnames
* constant
* diagnostics
* fields
* filetest
* integer
* less
* lib
* locale
* lwpcook
* open
* ops
* overload
* perllocal
* re
* sigtrap
* strict
* subs
* utf8
* vars
* warnings

Libraries


* ActivePerl
    * DocTools
        * TOC
            * RDF
* AnyDBM_File
* Archive
    * Tar
* AutoLoader
* AutoSplit
* B
    * Asmdata
    * Assembler
    * Bblock
    * Bytecode
    * C
    * CC
    * Debug
    * Deparse
    * Disassembler
    * Lint
    * Showlex
    * Stackobj
    * Terse
    * Xref
* Benchmark
* Bundle
    * LWP
* ByteLoader
* Carp
    * Heavy
* CGI
    * Apache
    * Carp
    * Cookie
    * Fast
    * Pretty
    * Push
    * Switch
* Class
    * Struct
* Compress
    * Zlib
* Config
* CPAN
    * FirstTime
    * Nox
* Cwd
* Data
    * Dumper
* DB
* Devel
    * DProf
    * Peek
    * SelfStubber
* Digest
    * HMAC
    * HMAC_MD5
    * HMAC_SHA1
    * MD2
    * MD5
    * SHA1
* DirHandle
* Dumpvalue
* DynaLoader
* English
* Env
* Errno
* Exporter
    * Heavy
* ExtUtils
    * Command
    * Embed
    * Install
    * Installed
    * Liblist
    * MakeMaker
    * Manifest
    * Miniperl
    * Mkbootstrap
    * Mksymlists
    * MM_Cygwin
    * MM_OS2
    * MM_Unix
    * MM_VMS
    * MM_Win32
    * Packlist
    * testlib
* Fatal
* Fcntl
* File
    * Basename
    * CheckTree
    * Compare
    * Copy
    * CounterFile
    * DosGlob
    * Find
    * Glob
    * Listing
    * Path
    * Spec
        * Functions
        * Mac
        * OS2
        * Unix
        * VMS
        * Win32
    * stat
* FileCache
* FileHandle
* FindBin
* Font
    * AFM
* Getopt
    * Long
    * Std
* HTML
    * AsSubs
    * Element
    * Entities
    * Filter
    * Form
    * FormatPS
    * Formatter
    * FormatText
    * HeadParser
    * LinkExtor
    * Parse
    * Parser
    * TokeParser
    * TreeBuilder
* HTTP
    * Cookies
    * Daemon
    * Date
    * Headers
        * Util
    * Message
    * Negotiate
    * Request
        * Common
    * Response
    * Status
* I18N
    * Collate
* IO
    * Dir
    * File
    * Handle
    * Pipe
    * Poll
    * Seekable
    * Select
    * Socket
        * INET
        * UNIX
* IPC
    * Msg
    * Open2
    * Open3
    * Semaphore
    * SysV
* LWP
    * Debug
    * MediaTypes
    * MemberMixin
    * Protocol
    * RobotUA
    * Simple
    * UserAgent
* Math
    * BigFloat
    * BigInt
    * Complex
    * Trig
* MD5
* MIME
    * Base64
    * QuotedPrint
* NDBM_File
* Net
    * Cmd
    * Config
    * Domain
    * DummyInetd
    * FTP
    * hostent
    * libnetFAQ
    * netent
    * Netrc
    * NNTP
    * PH
    * Ping
    * POP3
    * protoent
    * servent
    * SMTP
    * SNPP
    * Time
* O
* ODBM_File
* Opcode
* Pod
    * Checker
    * Find
    * Html
    * InputObjects
    * Man
    * Parser
    * ParseUtils
    * Plainer
    * Select
    * Text
        * Color
        * Termcap
    * Usage
* POSIX
* PPM
    * SOAPClient
    * SOAPServer
* Safe
* SDBM_File
* Search
    * Dict
* SelectSaver
* SelfLoader
* SHA
* Shell
* SOAP
    * Defs
    * Envelope
    * EnvelopeMaker
    * GenericHashSerializer
    * GenericInputStream
    * GenericScalarSerializer
    * Lite
    * OutputStream
    * Packager
    * Parser
    * Transport
        * HTTP
            * Apache
            * CGI
            * Client
            * Server
        * LOCAL
        * MAILTO
        * POP3
        * TCP
    * TypeMapper
* Socket
* Symbol
* Sys
    * Hostname
    * Syslog
* Term
    * ANSIColor
    * Cap
    * Complete
    * ReadLine
* Test
    * Harness
* Text
    * Abbrev
    * ParseWords
    * Soundex
    * Tabs
    * Wrap
* Thread
    * Queue
    * Semaphore
    * Signal
    * Specific
* Tie
    * Array
    * Handle
    * Hash
    * RefHash
    * Scalar
    * SubstrHash
* Time
    * gmtime
    * Local
    * localtime
    * tm
* UDDI
    * Lite
* UNIVERSAL
* URI
    * data
    * Escape
    * file
    * Heuristic
    * ldap
    * URL
    * WithBase
* User
    * grent
    * pwent
* Win32
    * AuthenticateUser
    * ChangeNotify
    * Clipboard
    * Console
    * Event
    * EventLog
    * File
    * FileSecurity
    * Internet
    * IPC
    * Mutex
    * NetAdmin
    * NetResource
    * ODBC
    * OLE
        * Const
        * Enum
        * NEWS
        * NLS
        * TPJ
        * Variant
    * PerfLib
    * Pipe
    * Process
    * Registry
    * Semaphore
    * Service
    * Sound
    * TieRegistry
* Win32API
    * File
    * Net
    * Registry
* WWW
    * RobotRules
        * AnyDBM_File
* XML
    * Element
    * Parser
        * Expat
    * PPD
    * PPMConfig
    * ValidatingElement
* XSLoader

 Date::Manip - date manipulation routines


NAME

Date::Manip - date manipulation routines


SUPPORTED PLATFORMS

  • Windows
This module is not included with the standard ActivePerl distribution. It is available as a separate download using PPM.

SYNOPSIS

 use Date::Manip;
 $date=&ParseDate(\@args)
 $date=&ParseDate($string)
 $date=&ParseDate(\$string)
 @date=&UnixDate($date,@format)
 $date=&UnixDate($date,@format)
 $delta=&ParseDateDelta(\@args)
 $delta=&ParseDateDelta($string)
 $delta=&ParseDateDelta(\$string)
 @str=&Delta_Format($delta,$dec,@format)
 $str=&Delta_Format($delta,$dec,@format)
 $recur=&ParseRecur($string,$base,$date0,$date1,$flags)
 @dates=&ParseRecur($string,$base,$date0,$date1,$flags)
 $d=&DateCalc($d1,$d2 [,$errref] [,$del])
 $date=&Date_SetTime($date,$hr,$min,$sec)
 $date=&Date_SetTime($date,$time)
 $date=&Date_SetDateField($date,$field,$val [,$nocheck])
 $date=&Date_GetPrev($date,$dow,$today,$hr,$min,$sec)
 $date=&Date_GetPrev($date,$dow,$today,$time)
 $date=&Date_GetNext($date,$dow,$today,$hr,$min,$sec)
 $date=&Date_GetNext($date,$dow,$today,$time)
 &Date_Init()
 &Date_Init("VAR=VAL",...)
 $version=&DateManipVersion
 $flag=&Date_IsWorkDay($date [,$flag]);
 $date=&Date_NextWorkDay($date,$off [,$time]);
 $date=&Date_PrevWorkDay($date,$off [,$time]);

The following routines are used by the above routines (though they can also be called directly). $y may be entered as either a 2 or 4 digit year (it will be converted to a 4 digit year based on the variable YYtoYYYY described below). Month and day should be numeric in all cases. Most (if not all) of the information below can be gotten from UnixDate which is really the way I intended it to be gotten, but there are reasons to use these (these are significantly faster).

 $day=&Date_DayOfWeek($m,$d,$y)
 $secs=&Date_SecsSince1970($m,$d,$y,$h,$mn,$s)
 $secs=&Date_SecsSince1970GMT($m,$d,$y,$h,$mn,$s)
 $days=&Date_DaysSince999($m,$d,$y)
 $day=&Date_DayOfYear($m,$d,$y)
 $days=&Date_DaysInYear($y)
 $wkno=&Date_WeekOfYear($m,$d,$y,$first)
 $flag=&Date_LeapYear($y)
 $day=&Date_DaySuffix($d)
 $tz=&Date_TimeZone()
 ($y,$m,$d,$h,$mn,$s)=&Date_NthDayOfYear($y,$n)


DESCRIPTION

This is a set of routines designed to make any common date/time manipulation easy to do. Operations such as comparing two times, calculating a time a given amount of time from another, or parsing international times are all easily done. From the very beginning, the main focus of Date::Manip has been to be able to do ANY desired date/time operation easily, not necessarily quickly. Also, it is definitely oriented towards the type of operationw we (as people) tend to think of rather than those operations used routinely by computers. There are other modules that can do a small subset of the operations available in Date::Manip much quicker than those presented here, so if speed is a primary issue, you should look elsewhere. Check out the CPAN listing of Time and Date modules. But for sheer flexibility, I believe that Date::Manip is your best bet.

Date::Manip deals with time as it is presented the Gregorian calendar (the one currently in use). The Julian calendar defined leap years as every 4th year. The Gregorian calendar improved this by making every 100th year NOT a leap year, unless it was also the 400th year. The Gregorian calendar has been extrapolated back to the year 1000 AD and forward to the year 9999 AD. Note that in historical context, the Julian calendar was in use until 1582 when the Gregorian calendar was adopted by the Catholic church. Protestant countries did not accept it until later; Germany and Netherlands in 1698, British Empire in 1752, Russia in 1918. Note that the Gregorian calendar is itself imperfect. Each year is on average 26 seconds too long, which means that every 3,323 years, a day should be removed from the calendar. No attempt is made to correct for that.

Date::Manip is therefore not equipped to truly deal with historical dates, but should be able to perform (virtually) any operation dealing with a modern time and date.

Date::Manip has (or will have) functionality to work with several fundamental types of data.

DATE
Although the word date is used extensively here, it is actually somewhat misleading. Date::Manip works with the full date AND time (year, month, day, hour, minute, second and weeks when appropriate). It doesn't work with fractional seconds. Timezones are also supported to some extent.

NOTE: Much better support for timezones (including Daylight Savings Time) is planned for the future.

DELTA
This refers to a duration or elapsed time. One thing to note is that, as used in this module, a delta refers only to the amount of time elapsed. It includes no information about a starting or ending time.

RECURRENCE
A recurrence is simply a notation for defining when a recurring event occurs. For example, if an event occurs every other Friday or every 4 hours, this can be defined as a recurrence. With a recurrence and a starting and ending date, you can get a list of dates in that period when a recurring event occurs.

GRAIN
The granularity of a time basically refers to how accurate you wish to treat a date. For example, if you want to compare two dates to see if they are identical at a granularity of days, then they only have to occur on the same day. At a granularity of an hour, they have to occur within an hour of each other, etc.

NOTE: Support for this will be added in the future.

Among other things, Date::Manip allow you to:

1. Enter a date and be able to choose any format conveniant

2. Compare two dates, entered in widely different formats to determine which is earlier

3. Extract any information you want from ANY date using a format string similar to the Unix date command

4. Determine the amount of time between two dates

5. Add a time offset to a date to get a second date (i.e. determine the date 132 days ago or 2 years and 3 months after Jan 2, 1992)

6. Work with dates with dates using international formats (foreign month names, 12/10/95 referring to October rather than December, etc.).

7. To find a list of dates where a recurring event happens.

Each of these tasks is trivial (one or two lines at most) with this package.


EXAMPLES

In the documentation below, US formats are used, but in most (if not all) cases, a non-English equivalent will work equally well.

1. Parsing a date from any conveniant format

  $date=&ParseDate("today");
  $date=&ParseDate("1st thursday in June 1992");
  $date=&ParseDate("05/10/93");
  $date=&ParseDate("12:30 Dec 12th 1880");
  $date=&ParseDate("8:00pm december tenth");
  if (! $date) {
    # Error in the date
  }

2. Compare two dates

  $date1=&ParseDate($string1);
  $date2=&ParseDate($string2);
  if ($date1 lt $date2) {
    # date1 is earlier
  } else {
    # date2 is earlier (or the two dates are identical)
  }

3. Extract information from a date.

  print &UnixDate("today","The time is now %T on %b %e, %Y.");
  =>  "The time is now 13:24:08 on Feb  3, 1996."

4. The amount of time between two dates.

  $date1=&ParseDate($string1);
  $date2=&ParseDate($string2);
  $delta=&DateCalc($date1,$date2,\$err);
  => 0:0:WK:DD:HH:MM:SS   the weeks, days, hours, minutes, and seconds
                          between the two
  $delta=&DateCalc($date1,$date2,\$err,1);
  => YY:MM:WK:DD:HH:MM:SS  the years, months, etc. between the two
  Read the documentation below for an explanation of the difference.

5. To determine a date a given offset from another.

  $date=&DateCalc("today","+ 3hours 12minutes 6 seconds",\$err);
  $date=&DateCalc("12 hours ago","12:30 6Jan90",\$err);
  It even works with business days:
  $date=&DateCalc("today","+ 3 business days",\$err);

6. To work with dates in another language.

  &Date_Init("Language=French","DateFormat=non-US");
  $date=&ParseDate("1er decembre 1990");

7. To find a list of dates where a recurring event happens.

  # To find the 2nd tuesday of every month
  @date=&ParseRecur("0:1*2:2:0:0:0",$base,$start,$stop);

NOTE: Some date forms do not work as well in languages other than English, but this is not because DateManip is incapable of doing so (almost nothing in this module is language dependent). It is simply that I do not have the correct translation available for some words. If there is a date form that works in English but does not work in a language you need, let me know and if you can provide me the translation, I will fix DateManip.


SHOULD I USE DATE::MANIP

If you look in CPAN, you'll find that there are a number of Date and Time packages. Is Date::Manip the one you should be using?

Date::Manip has several strengths. These include flexibility, a wide variety of functions, and it is written entirely in perl.

It also has several weaknesses. The main one is that it is written entirely in perl.

The fact that it is written in perl is both an advantage and a disadvantage. It means that you are not required to have a C compiler around in order to install Date::Manip (in fact, Date::Manip has no dependancies on anything not included in a standard perl distribution since perl 5.002 or so). On Unix platforms, this is not terribly important since they pretty much all have a C compiler, but on non-Unix platforms, this can simplify insallation.

The downside is that Date::Manip is slow, especially when compared to several of the other Date/Time modules which are written in C. Although I am working on making Date::Manip faster, it will never be as fast as these modules. And before anyone asks, Date::Manip will never be translated to C (at least by me). I write C because I have to. I write perl because I like to. Date::Manip is something I do because it interests me, not something I'm paid for.

If you are going to be using the module in cases where performance is an important factor (parsing 10,000 dates from a database or started up in a CGI program being run by your web server 5,000 times a second), you might check out one of the other Date or Time modules in CPAN. Date::DateCalc, Date::TimeDate, or Time::Time-modules might meet your needs. In general, you do not need the flexibility offered by Date::Manip in these cases. For example, if you are reading a database, all of the dates are written in exactly the same format. It should be trivial to write a routine specific to this format.

The biggest strength of Date::Manip is it's flexibility. None of the other modules can do everything that Date::Manip can do. I'm trying to build a library which can do _EVERY_ conceivable date/time manipulation that you'll run into in everyday life. It is definitely intended to use in the terms of how you (not the computer) think of dates and times.

If you are doing operations based more on how people think of dates and times, Date::Manip is almost certainly for you. This includes parsing dates (including foreign language dates), calendar type operations, business dates and holidays, etc.


ROUTINES

ParseDate
 $date=&ParseDate(\@args)
 $date=&ParseDate($string)
 $date=&ParseDate(\$string)

This takes an array or a string containing a date and parses it. When the date is included as an array (for example, the arguments to a program) the array should contain a valid date in the first one or more elements (elements after a valid date are ignored). Elements containing a valid date are shifted from the array. The largest possible number of elements which can be correctly interpreted as a valid date are always used. If a string is entered rather than an array, that string is tested for a valid date. The string is unmodified, even if passed in by reference.

The real work is done in the ParseDateString routine.

The ParseDate routine is primarily used to handle command line arguments. If you have a command where you want to enter a date as a command line arguement, you can use Date::Manip to make something like the following work:

  mycommand -date Dec 10 1997 -arg -arg2

No more reading man pages to find out what date format is required in a man page.

Historical note: this is originally why the Date::Manip routines were written. I was using a bunch of programs where dates and times were entered as command line options and I was getting highly annoyed at the many different (but not compatible) ways that they could be entered.

ParseDateString
 $date=&ParseDateString($string)

This routine is called by ParseDate, but it may also be called directly to save some time.

NOTE: One of the most frequently asked questions that I have gotten is how to parse seconds since the epoch. ParseDateString cannot simply parse a number as the seconds since the epoch (it conflicts with some ISO-8601 date formats). There are two ways to get this information. First, you can do the following:

    $secs = ...         # seconds since Jan 1, 1970  00:00:00 GMT
    $date = &DateCalc("Jan 1, 1970  00:00:00 GMT",$secs);

Second, you can call it directly as:

    $date = &ParseDateString("epoch $secs");

To go backwards, just use the ``%s'' format of UnixDate:

    $secs = &UnixDate($date,"%s");

A date actually includes 2 parts: date and time. A time must include hours and minutes and can optionally include seconds, fractional seconds, an am/pm type string, and a timezone. For example:

     [at] HH:MN              [Zone]
     [at] HH:MN         [am] [Zone]
     [at] HH:MN:SS      [am] [Zone]
     [at] HH:MN:SS.SSSS [am] [Zone]
     [at] HH            am   [Zone]

Hours can be written using 1 or 2 digits, but the single digit form may only be used when no ambiguity is introduced (i.e. when it is not immediately preceded by a digit).

A time is usually entered in 24 hour mode, but 12 hour mode can be used as well if AM/PM are entered (AM can be entered as AM or A.M. or other variations depending on the language).

Fractional seconds are also supported in parsing but the fractional part is discarded.

Timezones always appear after the time. A number of different forms are supported (see the section TIMEZONEs below).

Spaces (or other separators such as ``/'' or ``-'') in the date are always optional when there is absolutely no ambiguity if they are not present. If there is ambiguity, the date will either be unparsable, or (as is more often the case) get parsed differently than desired.

Years can be entered as 2 or 4 digits, days and months as 1 or 2 digits. Both days and months must include 2 digits whenver they are immediately adjacent to another part of the date or time.

Incidentally, the time is removed from the date before the date is parsed, so the time may appear before or after the date, or between any two parts of the date.

Sections of the date may be separated by spaces or by other valid date separators (including ``/'', ``.'', and in some cases ``-''). These separators are treated very flexibly (they are converted to spaces), so the following dates are all equivalent:

   12/10/1965
   12-10 / 1965
   12 // 10 -. 1965

In some cases, this may actually be TOO flexible, but no attempt is made to trap this.

Valid date formats include the ISO 8601 formats:

   YYYYMMDDHHMNSSFFFF
   YYYYMMDDHHMNSS
   YYYYMMDDHHMN
   YYYYMMDDHH
   YY-MMDDHHMNSSF...
   YY-MMDDHHMNSS
   YY-MMDDHHMN
   YY-MMDDHH
   YYYYMMDD
   YYYYMM
   YYYY
   YY-MMDD
   YY-MM
   YY
   YYYYwWWD      ex.  1965-W02-2
   YYwWWD
   YYYYDOY       ex.  1965-045
   YYDOY

In the above list, YYYY and YY signify 4 or 2 digit years, MM, DD, HH, MN, SS refer to two digit month, day, hour, minute, and second respectively. F... refers to fractional seconds (any number of digits) which will be ignored. The last 4 formats can be explained by example: 1965-w02-2 refers to Tuesday (day 2) of the 2nd week of 1965. 1965-045 refers to the 45th day of 1965.

In all cases, parts of the date may be separated by dashes ``-''. If this is done, 1 or 2 digit forms of MM, DD, etc. may be used. All dashes are optional except for those given in the table above (which MUST be included for that format to be correctly parsed).

NOTE: Even though not allowed in the standard, the timezone for an ISO-8601 date is flexible and may be any of the timezones understood by Date::Manip.

Additional date formats are available which may or may not be common including:

  MM/DD  **
  MM/DD/YY  **
  MM/DD/YYYY  **
  mmmDD       DDmmm                   mmmYYYY/DD
  mmmDDYY     DDmmmYY     DDYYmmm     YYYYmmmDD
  mmmDDYYYY   DDmmmYYYY   DDYYYYmmm   YYYY/DDmmm

Where mmm refers to the name of a month. All parts of the date can be separated by valid separators (space, ``/'', ``.'', or ``-'' as long as it doesn't conflict with an ISO 8601 format), but these are optional except for those given as a ``/'' in the list above.

** Note that with these formats, Americans tend to write month first, but many other contries tend to write day first. The latter behavior can be obtained by setting the config variable DateFormat to something other than ``US'' (see CUSTOMIZING DATE::MANIP below).

Miscellaneous other allowed formats are: which dofw in mmm in YY ``first sunday in june 1996 at 14:00'' dofw week num YY ``sunday week 22 1995'' which dofw YY ``22nd sunday at noon'' dofw which week YY ``sunday 22nd week in 1996'' next/last dofw ``next friday at noon'' next/last week/month ``next month'' in num days/weeks/months ``in 3 weeks at 12:00'' num days/weeks/months later ``3 weeks later'' num days/weeks/months ago ``3 weeks ago'' dofw in num week ``Friday in 2 weeks'' in num weeks dofw ``in 2 weeks on friday'' dofw num week ago ``Friday 2 weeks ago'' num week ago dofw ``2 weeks ago friday'' last day in mmm in YY ``last day of October'' dofw ``Friday'' (Friday of current week) Nth ``12th'', ``1st'' (day of current month) ecpoch SECS seconds since the epoch

Note that certain words such as ``in'', ``at'', ``of'', etc. which commonly appear in a date or time are ignored. Also, the year is alway optional.

In addition, the following strings are recognized: today now (synonym for today) yesterday (exactly 24 hours ago) tomorrow (exactly 24 hours from now) noon (12:00:00) midnight (00:00:00) Other languages have similar (and in some cases additional) strings.

Some things to note:

All strings are case insensitive. ``December'' and ``DEceMBer'' both work.

When a part of the date is not given, defaults are used: year defaults to current year; hours, minutes, seconds to 00.

The year may be entered as 2 or 4 digits. If entered as 2 digits, it must first be converted to a 4 digit year. There are a couple of ways to do this based on the value of the YYtoYYYY variable (described below). The default behavior it to force the 2 digit year to be in the 100 year period CurrYear-89 to CurrYear+10. So in 1996, the range is [1907 to 2006], so the 2 digit year 05 would refer to 2005 but 07 would refer to 1907. See CUSTOMIZING DATE::MANIP below for information on YYtoYYYY for other methods.

Dates are always checked to make sure they are valid.

In all of the formats, the day of week (``Friday'') can be entered anywhere in the date and it will be checked for accuracy. In other words, ``Tue Jul 16 1996 13:17:00'' will work but ``Jul 16 1996 Wednesday 13:17:00'' will not (because Jul 16, 1996 is Tuesday, not Wednesday). Note that depending on where the weekday comes, it may give unexpected results when used in array context (with ParseDate). For example, the date (``Jun'',``25'',``Sun'',``1990'') would return June 25 of the current year since Jun 25, 1990 is not Sunday.

The times ``12:00 am'', ``12:00 pm'', and ``midnight'' are not well defined. For good or bad, I use the following convention in Date::Manip: midnight = 12:00am = 00:00:00 noon = 12:00pm = 12:00:00 and the day goes from 00:00:00 to 23:59:59. In otherwords, midnight is the beginning of a day rather than the end of one. The time 24:00:00 is NOT allowed (even though ISO 8601 allows it).

The format of the date returned is YYYYMMDDHH:MM:SS. The advantage of this time format is that two times can be compared using simple string comparisons to find out which is later. Also, it is readily understood by a human. Alternate forms can be used if that is more conveniant. See Date_Init below and the config variable Internal.

NOTE: The format for the date is going to change at some point in the future to YYYYMMDDHH:MN:SS+HHMN (i.e. it'll include the timezone). In order to maintain compatibility, you should use UnixDate to extract information from a date.

UnixDate
 @date=&UnixDate($date,@format)
 $date=&UnixDate($date,@format)

This takes a date and a list of strings containing formats roughly identical to the format strings used by the UNIX date(1) command. Each format is parsed and an array of strings corresponding to each format is returned.

$date may be any string that can be parsed by ParseDateString.

The format options are:

 Year
     %y     year                     - 00 to 99
     %Y     year                     - 0001 to 9999
     %G     year                     - 0001 to 9999 (see below)
     %L     year                     - 0001 to 9999 (see below)
 Month, Week
     %m     month of year            - 01 to 12
     %f     month of year            - " 1" to "12"
     %b,%h  month abbreviation       - Jan to Dec
     %B     month name               - January to December
     %U     week of year, Sunday
            as first day of week     - 01 to 53
     %W     week of year, Monday
            as first day of week     - 01 to 53
 Day
     %j     day of the year          - 001 to 366
     %d     day of month             - 01 to 31
     %e     day of month             - " 1" to "31"
     %v     weekday abbreviation     - " S"," M"," T"," W","Th"," F","Sa"
     %a     weekday abbreviation     - Sun to Sat
     %A     weekday name             - Sunday to Saturday
     %w     day of week              - 1 (Monday) to 7 (Sunday)
     %E     day of month with suffix - 1st, 2nd, 3rd...
 Hour
     %H     hour                     - 00 to 23
     %k     hour                     - " 0" to "23"
     %i     hour                     - " 1" to "12"
     %I     hour                     - 01 to 12
     %p     AM or PM
 Minute, Second, Timezone
     %M     minute                   - 00 to 59
     %S     second                   - 00 to 59
     %s     seconds from 1/1/1970 GMT- negative if before 1/1/1970
     %o     seconds from Jan 1, 1970
            in the current time zone
     %z,%Z  timezone (3 characters)  - "EDT"
 Date, Time
     %c     %a %b %e %H:%M:%S %Y     - Fri Apr 28 17:23:15 1995
     %C,%u  %a %b %e %H:%M:%S %z %Y  - Fri Apr 28 17:25:57 EDT 1995
     %g     %a, %d %b %Y %H:%M:%S %z - Fri, 28 Apr 1995 17:23:15 EDT
     %D,%x  %m/%d/%y                 - 04/28/95
     %l     date in ls(1) format
              %b %e $H:$M            - Apr 28 17:23  (if within 6 months)
              %b %e  %Y              - Apr 28  1993  (otherwise)
     %r     %I:%M:%S %p              - 05:39:55 PM
     %R     %H:%M                    - 17:40
     %T,%X  %H:%M:%S                 - 17:40:58
     %V     %m%d%H%M%y               - 0428174095
     %Q     %Y%m%d                   - 19961025
     %q     %Y%m%d%H%M%S             - 19961025174058
     %P     %Y%m%d%H%M%S             - 1996102517:40:58
     %F     %A, %B %e, %Y            - Sunday, January  1, 1996
     %J     %G-W%W-%w                - 1997-W02-2
     %K     %Y-%j                    - 1997-045
 Other formats
     %n     insert a newline character
     %t     insert a tab character
     %%     insert a `%' character
     %+     insert a `+' character
 The following formats are currently unused but may be used in the future:
     NO 1234567890 !@#$^&*()_|-=\`[];',./~{}:<>?
 They currently insert the character following the %, but may (and probably
 will) change in the future as new formats are added.

If a lone percent is the final character in a format, it is ignored.

Note that the ls format (%l) applies to date within the past OR future 6 months!

The formats %U and %W return a week from 01 to 53. Because days at the beginning or end of the year may actually appear in a week in the previous or next year, the %L and %G formats were added to handle this case. %L and %G give the year of the week for %U and %W respectively. So Jan 1, 1993 is written in ISO-8601 format as 1992-W53-5. In this case, %Y is 1993, but %G is 1992 and %W is 53. %L and %U are similar for weeks starting with Sunday. %J returns the full ISO-8601 format.

Note that the %s format was introduced in version 5.07. Prior to that, %s referred to the seconds since 1/1/70. This was moved to %o in 5.07.

The formats used in this routine were originally based on date.pl (version 3.2) by Terry McGonigal, as well as a couple taken from different versions of the date(1). Also, several have been added which are unique to Date::Manip.

ParseDateDelta
 $delta=&ParseDateDelta(\@args)
 $delta=&ParseDateDelta($string)
 $delta=&ParseDateDelta(\$string)

This takes an array and shifts a valid delta date (an amount of time) from the array. Recognized deltas are of the form: +Yy +Mm +Ww +Dd +Hh +MNmn +Ss examples: +4 hours +3mn -2second + 4 hr 3 minutes -2 4 hour + 3 min -2 s +Y:+M:+W:+D:+H:+MN:+S examples: 0:0:0:0:4:3:-2 +4:3:-2 mixed format examples: 4 hour 3:-2

A field in the format +Yy is a sign, a number, and a string specifying the type of field. The sign is ``+'', ``-'', or absent (defaults to the next larger element). The valid strings specifying the field type are: y: y, yr, year, years m: m, mon, month, months w: w, wk, ws, wks, week, weeks d: d, day, days h: h, hr, hour, hours mn: mn, min, minute, minutes s: s, sec, second, seconds

Also, the ``s'' string may be omitted. The sign, number, and string may all be separated from each other by any number of whitespaces.

In the date, all fields must be given in the order: Y M W D H MN S. Any number of them may be omitted provided the rest remain in the correct order. In the 2nd (colon) format, from 2 to 7 of the fields may be given. For example +D:+H:+MN:+S may be given to specify only four of the fields. In any case, both the MN and S field may be present. No spaces may be present in the colon format.

Deltas may also be given as a combination of the two formats. For example, the following is valid: +Yy +D:+H:+MN:+S. Again, all fields must be given in the correct order.

The word ``in'' may be prepended to the delta (``in 5 years'') and the word ``ago'' may be appended (``6 months ago''). The ``in'' is completely ignored. The ``ago'' has the affect of reversing all signs that appear in front of the components of the delta. I.e. ``-12 yr 6 mon ago'' is identical to ``+12yr +6mon'' (don't forget that there is an impled minus sign in front of the 6 because when no sign is explicitely given, it carries the previously entered sign).

One thing is worth noting. The year/month and day/hour/min/sec parts are returned in a ``normalized'' form. That is, the signs are adjusted so as to be all positive or all negative. For example, ``+ 2 day - 2hour'' does not return ``0:0:0:2:-2:0:0''. It returns ``+0:0:0:1:22:0:0'' (1 day 22 hours which is equivalent). I find (and I think most others agree) that this is a more useful form.

Since the year/month and day/hour/min/sec parts must be normalized separately there is the possibility that the sign of the two parts will be different. So, the delta ``+ 2years -10 months - 2 days + 2 hours'' produces the delta ``+1:2:-0:1:22:0:0''.

It is possible to include a sign for all elements that is output. See the configuration variable DeltaSigns below.

NOTE: The internal format of the delta changed in version 5.30 from Y:M:D:H:MN:S to Y:M:W:D:H:MN:S . Also, it is going to change again at some point in the future to Y:M:W:D:H:MN:S*FLAGS . Use the routine Delta_Format to extract information rather than parsing it yourself.

Delta_Format
 @str=&Delta_Format($delta,$dec,@format)
 $str=&Delta_Format($delta,$dec,@format)

This is similar to the UnixDate routine except that it extracts information from a delta. Unlike the UnixDate routine, most of the formats are 2 characters instead of 1.

NOTE: For the time being, Delta_Format only understands the ``exact'' parts of a delta (Y/M) and (W/D/H/MN/S). There is currently no ``mixing'' between the two parts.

Formats currently understood are:

   %Xv     : the value of the field named X
   %Xd     : the value of the field X, and all smaller fields, expressed in
             units of X
   %Xh     : the value of field X, and all larger fields, expressed in units
             of X
   %Xt     : the value of all fields expressed in units of X
   X is one of y,M,w,d,h,m,s (case sensitive).
   %%      : returns a "%"

So, the format ``%hd'' means the values of H, MN, and S expressed in hours. So for the delta ``0:0:0:0:2:30:0'', this format returns 2.5. Similarily, the format ``%yd'' means the value (in years) of both the Y and M fields.

The format ``%hh'' returns the value of W, D, and H expressed in hours.

If $dec is non-zero, the %Xd and %Xt values are formatted to contain $dec decimal places.

ParseRecur
 $recur=&ParseRecur($string [,$base,$date0,$date1,$flags])
 @dates=&ParseRecur($string [,$base,$date0,$date1,$flags])

A recurrence refers to a recurring event. A fully specified recurrence requires (in most cases) 4 items: a recur description (describing the frequency of the event), a base date (a date when the event occurred and which other occurences are based on), and a start and end date. There may be one or more flags included which modify the behavior of the recur description. It is written as:

  recur*flags*base*date0*date1

Here, base, date0, and date1 are any strings (which must not contain any asterixes) which can be parsed by ParseDate. flags is a comma separated list of flags (described below), and recur is a string describing a recurring event.

If called in scalar context, it returns a string containing a fully specified recurrence (or as much of it as can be determined with unspecified fields left blank). In list context, it returns a list of all dates referred to by a recurrence if enough information is given in the recurrence. All dates returned are in the range:

  date0 <= date < date1

The argument $string can contain any of the parts of a full recurrence. For example:

  recur
  recur*flags
  recur**base*date0*date1

The only part which is required is the recur description. Any values contained in $string are overridden by values passed in as parameters to ParseRecur.

A recur description is a string of the format Y:M:W:D:H:MN:S . Exactly one of the colons may optionally be replaced by an asterix, or an asterix may be prepended to the string.

Any value ``N'' to the left of the asterix refers to the ``Nth'' one. Any value to the right of the asterix refers to a value as it appears on a calendar. These can be a value or a comma separated list of values or ranges. In a few cases, negative values are appropriate.

This is best illustrated by example.

  0:0:2:1:0:0:0        every 2 weeks and 1 day
  0:0:0:0:5:30:0       every 5 hours and 30 minutes
  0:0:0:2*12:30:0      every 2 days at 12:30 (each day)
  3*1:0:2:12:0:0       every 3 years on Jan 2 at noon
  0:1*0:2:12,14:0:0    2nd of every month at 12:00 and 14:00
  1:0:0*45:0:0:0       45th day of every year
  0:1*4:2:0:0:0        4th tuesday (day 2) of every month
  0:1*-1:2:0:0:0       last tuesday of every month
  0:1:0*-2:0:0:0       2nd to last day of every month
  0:0:3*2:0:0:0        every 3rd tuesday (every 3 weeks on 2nd day of week)
  1:0*12:2:0:0:0       tuesday of the 12th week of each year
  *1990-1995:12:0:1:0:0:0
                       Dec 1 in 1990 through 1995
  0:1*2:0:0:0:0        the start of the 2nd week of every month (see Note 2)
  1*1:2:0:0:0:0        the start of the 2nd week in January each year (Note 2)

Note 1: There is no way to express the following with a single recurrence:

  every day at 12:30 and 1:00

Note 2: A recurrence specifying the week of a month is NOT clearly defined in common usage. What is the 1st week in a month? The behavior (with respect to this module) is well defined (using some of the flags below), but in common usage, this is so ambiguous that this form should probably never be used.

Note 3: Depending on whether M and W are 0 or nonzero, D means different things. This is given in the following table.

  M  W  D (when right of an asterix) refers to
  -  -  -------------------------------------------
  0  0  day of year (1-366)
  M  0  day of month (1-31)
  0  W  day of week (1-7),  W refers to the week of year
  M  W  the Wth (1-5 or -1 to -5) occurence of Dth (1-7) day of week in month

There are a small handful of English strings which can be parsed in place of a numerical recur description. These include:

  every 2nd day [in 1997]
  every 2nd day in June [1997]
  2nd day of every month [in 1997]
  2nd tuesday of every month [in 1997]
  last tuesday of every month [in 1997]
  every 2nd tuesday [in 1997]
  every 2nd tuesday in June [1997]

Each of these set base, date0, and date1 to a default value (the current year with Jan 1 being the base date is the default if the year and month are missing).

Flags are not yet implemented, but will allow even more complex behaviors to be easily defined.

DateCalc
 $d=&DateCalc($d1,$d2 [,\$err] [,$mode])

This takes two dates, deltas, or one of each and performs the appropriate calculation with them. Dates must be a string that can be parsed by &ParseDateString. Deltas must be a string that can be parsed by &ParseDateDelta. Two deltas add together to form a third delta. A date and a delta returns a 2nd date. Two dates return a delta (the difference between the two dates).

Note that in many cases, it is somewhat ambiguous what the delta actually refers to. Although it is ALWAYS known how many months in a year, hours in a day, etc., it is NOT known how many days form a month. As a result, the part of the delta containing month/year and the part with sec/min/hr/day must be treated separately. For example, ``Mar 31, 12:00:00'' plus a delta of 1month 2days would yield ``May 2 12:00:00''. The year/month is first handled while keeping the same date. Mar 31 plus one month is Apr 31 (but since Apr only has 30 days, it becomes Apr 30). Apr 30 + 2 days is May 2. As a result, in the case where two dates are entered, the resulting delta can take on two different forms. By default ($mode=0), an absolutely correct delta (ignoring daylight savings time) is returned in days, hours, minutes, and seconds.

If $mode is 1, the math is done using an approximate mode where a delta is returned using years and months as well. The year and month part is calculated first followed by the rest. For example, the two dates ``Mar 12 1995'' and ``Apr 13 1995'' would have an exact delta of ``31 days'' but in the approximate mode, it would be returned as ``1 month 1 day''. Also, ``Mar 31'' and ``Apr 30'' would have deltas of ``30 days'' or ``1 month'' (since Apr 31 doesn't exist, it drops down to Apr 30). Approximate mode is a more human way of looking at things (you'd say 1 month and 2 days more often then 33 days), but it is less meaningful in terms of absolute time. In approximate mode $d1 and $d2 must be dates. If either or both is a delta, the calculation is done in exact mode.

If $mode is 2, a business mode is used. That is, the calculation is done using business days, ignoring holidays, weekends, etc. In order to correctly use this mode, a config file must exist which contains the section defining holidays (see documentation on the config file below). The config file can also define the work week and the hours of the work day, so it is possible to have different config files for different businesses.

For example, if a config file defines the workday as 08:00 to 18:00, a workweek consisting of Mon-Sat, and the standard (American) holidays, then from Tuesday at 12:00 to the following Monday at 14:00 is 5 days and 2 hours. If the ``end'' of the day is reached in a calculation, it autmoatically switches to the next day. So, Tuesday at 12:00 plus 6 hours is Wednesday at 08:00 (provided Wed is not a holiday). Also, a date that is not during a workday automatically becomes the start of the next workday. So, Sunday 12:00 and Monday at 03:00 both automatically becomes Monday at 08:00 (provided Monday is not a holiday). In business mode, any combination of date and delta may be entered, but a delta should not contain a year or month field (weeks are fine though).

See below for some additional comments about business mode calculations.

Any other non-nil value of $mode is treated as $mode=1 (approximate mode).

The mode can be automatically set in the dates/deltas passed by including a key word somewhere in it. For example, in English, if the word ``approximately'' is found in either of the date/delta arguments, approximate mode is forced. Likewise, if the word ``business'' or ``exactly'' appears, business/exact mode is forced (and $mode is ignored). So, the two following are equivalent:

   $date=&DateCalc("today","+ 2 business days",\$err);
   $date=&DateCalc("today","+ 2 days",\$err,2);

Note that if the keyword method is used instead of passing in $mode, it is important that the keyword actually appear in the argument passed in to DateCalc. The following will NOT work:

   $delta=&ParseDateDelta("+ 2 business days");
   $today=&ParseDate("today");
   $date=&DateCalc($today,$delta,\$err);

because the mode keyword is removed from a date/delta by the parse routines, and the mode is reset each time a parse routine is called. Since DateCalc parses both of its arguments, whatever mode was previously set is ignored.

If \$err is passed in, it is set to: 1 is returned if $d1 is not a delta or date 2 is returned if $d2 is not a delta or date 3 is returned if the date is outside the years 1000 to 9999 This argument is optional, but if included, it must come before $mode.

Nothing is returned if an error occurs.

When a delta is returned, the signs such that it is strictly positive or strictly negative (``1 day - 2 hours'' would never be returned for example). The only time when this cannot be enforced is when two deltas with a year/month component are entered. In this case, only the signs on the day/hour/min/sec part are standardized.

Date_SetTime
 $date=&Date_SetTime($date,$hr,$min,$sec)
 $date=&Date_SetTime($date,$time)

This takes a date (any string that may be parsed by ParseDateString) and sets the time in that date. For example, to get the time for 7:30 tomorrow, use the lines:

   $date=&ParseDate("tomorrow")
   $date=&Date_SetTime($date,"7:30")

Note that in this routine (as well as the other routines below which use a time argument), no real parsing is done on the times. As a result,

   $date=&Date_SetTime($date,"13:30")

works, but

   $date=&Date_SetTime($date,"1:30 PM")

doesn't.

Date_SetDateField
 $date=&Date_SetDateField($date,$field,$val [,$nocheck])

This takes a date and sets one of it's fields to a new value. $field is any of the strings ``y'', ``m'', ``d'', ``h'', ``mn'', ``s'' (case insensitive) and $val is the new value.

If $nocheck is non-zero, no check is made as to the validity of the date.

Date_GetPrev
 $date=&Date_GetPrev($date,$dow, $curr [,$hr,$min,$sec])
 $date=&Date_GetPrev($date,$dow, $curr [,$time])
 $date=&Date_GetPrev($date,undef,$curr,$hr,$min,$sec)
 $date=&Date_GetPrev($date,undef,$curr,$time)

This takes a date (any string that may be parsed by ParseDateString) and finds the previous occurence of either a day of the week, or a certain time of day.

If $dow is defined, the previous occurence of the day of week is returned. $dow may either be a string (such as ``Fri'' or ``Friday'') or a number (between 1 and 7). The date of the previous $dow is returned. If $date falls on this day of week, the date returned will be $date (if $curr is non-zero) or a week earlier (if $curr is 0). If a time is passed in (either as separate hours, minutes, seconds or as a time in HH:MM:SS or HH:MM format), the time on this date is set to it. The following examples should illustrate the use of Date_GetPrev:

    date                   dow    curr  time            returns
    Fri Nov 22 18:15:00    Thu    0     12:30           Thu Nov 21 12:30:00
    Fri Nov 22 18:15:00    Fri    0     12:30           Fri Nov 15 12:30:00
    Fri Nov 22 18:15:00    Fri    1     12:30           Fri Nov 22 12:30:00

If $dow is undefined, then a time must be entered, and the date returned is the previous occurence of this time. If $curr is non-zero, the current time is returned if it matches the criteria passed in. In other words, the time returned is the last time that a digital clock (in 24 hour mode) would have displayed the time you passed in. If you define hours, minutes and seconds default to 0 and you might jump back as much as an entire day. If hours are undefined, you are looking for the last time the minutes/seconds appeared on the digital clock, so at most, the time will jump back one hour.

    date               curr  hr     min    sec      returns
    Nov 22 18:15:00    0/1   18     undef  undef    Nov 22 18:00:00
    Nov 22 18:15:00    0/1   18     30     0        Nov 21 18:30:00
    Nov 22 18:15:00    0     18     15     undef    Nov 21 18:15:00
    Nov 22 18:15:00    1     18     15     undef    Nov 22 18:15:00
    Nov 22 18:15:00    0     undef  15     undef    Nov 22 17:15:00
    Nov 22 18:15:00    1     undef  15     undef    Nov 22 18:15:00
Date_GetNext
 $date=&Date_GetNext($date,$dow, $curr [,$hr,$min,$sec])
 $date=&Date_GetNext($date,$dow, $curr [,$time])
 $date=&Date_GetNext($date,undef,$curr,$hr,$min,$sec)
 $date=&Date_GetNext($date,undef,$curr,$time)

Similar to Date_GetPrev.

Date_DayOfWeek
 $day=&Date_DayOfWeek($m,$d,$y);

Returns the day of the week (0 for Sunday, 6 for Saturday). Dec 31, 0999 was Tuesday.

All arguments must be numeric.

Date_SecsSince1970
 $secs=&Date_SecsSince1970($m,$d,$y,$h,$mn,$s)

Returns the number of seconds since Jan 1, 1970 00:00 (negative if date is earlier).

All arguments must be numeric.

Date_SecsSince1970GMT
 $secs=&Date_SecsSince1970GMT($m,$d,$y,$h,$mn,$s)

Returns the number of seconds since Jan 1, 1970 00:00 GMT (negative if date is earlier). If CurrTZ is ``IGNORE'', the number will be identical to Date_SecsSince1970 (i.e. the date given will be treated as being in GMT).

All arguments must be numeric.

Date_DaysSince999
 $days=&Date_DaysSince999($m,$d,$y)

Returns the number of days since Dec 31, 0999.

All arguments must be numeric.

Date_DayOfYear
 $day=&Date_DayOfYear($m,$d,$y);

Returns the day of the year (001 to 366)

All arguments must be numeric.

Date_NthDayOfYear
 ($y,$m,$d,$h,$mn,$s)=&Date_NthDayOfYear($y,$n);

Returns the year, month, day, hour, minutes, and decimal seconds given a floating point day of the year.

All arguments must be numeric. $n must be greater than or equal to 1 and less than 366 on non-leap years and 367 on leap years.

Date_DaysInYear
 $days=&Date_DaysInYear($y);

Returns the number of days in the year (365 or 366)

Date_DaysInMonth
 $days=&Date_DaysInMonth($m,$y);

Returns the number of days in the month.

Date_WeekOfYear
 $wkno=&Date_WeekOfYear($m,$d,$y,$first);

Figure out week number. $first is the first day of the week which is usually 1 (Monday) or 7 (Sunday), but could be any number between 1 and 7 in practice.

All arguments must be numeric.

NOTE: This routine should only be called in rare cases. Use UnixDate with the %W, %U, %J, %L formats instead. This routine returns a week between 0 and 53 which must then be ``fixed'' to get into the ISO-8601 weeks from 1 to 53. A date which returns a week of 0 actually belongs to the last week of the previous year. A date which returns a week of 53 may belong to the first week of the next year.

Date_LeapYear
 $flag=&Date_LeapYear($y);

Returns 1 if the argument is a leap year Written by David Muir Sharnoff <muir@idiom.com>

Date_DaySuffix
 $day=&Date_DaySuffix($d);

Add `st', `nd', `rd', `th' to a date (ie 1st, 22nd, 29th). Works for international dates.

Date_TimeZone
 $tz=&Date_TimeZone

This returns a timezone. It looks in the following places for a timezone in the following order:

   $ENV{TZ}
   $main::TZ
   unix 'date' command
   /etc/TIMEZONE

If it's not found in any of those places, an error occurs:

   ERROR: Date::Manip unable to determine TimeZone.

Date_TimeZone is able to read zones of the format PST8PDT (see TIMEZONES documentation below).

Date_ConvTZ
 $date=&Date_ConvTZ($date)
 $date=&Date_ConvTZ($date,$from)
 $date=&Date_ConvTZ($date,(),$to)
 $date=&Date_ConvTZ($date,$from,$to)

This converts a date (which MUST be in the format returned by ParseDate) from one timezone to another.

If it is called with no arguments, the date is converted from the local timezone to the timezone specified by the config variable ConvTZ (see documentation on ConvTZ below). If ConvTZ is set to ``IGNORE'', no conversion is done.

If called with $from but no $to, the timezone is converted from the timezone in $from to ConvTZ (of TZ if ConvTZ is not set). Again, no conversion is done if ConvTZ is set to ``IGNORE''.

If called with $to but no $from, $from defaults to ConvTZ (if set) or the local timezone otherwise. Although this does not seem immediately obvious, it actually makes sense. By default, all dates that are parsed are converted to ConvTZ, so most of the dates being worked with will be stored in that timezone.

If Date_ConvTZ is called with both $from and $to, the date is converted from the timezone $from to $to.

NOTE: As in all other cases, the $date returned from Date_ConvTZ has no timezone information included as part of it, so calling UnixDate with the ``%z'' format will return the timezone that Date::Manip is working in (usually the local timezone).

Example: To convert 2/2/96 noon PST to CST (regardless of what timezone you are in, do the following:

 $date=&ParseDate("2/2/96 noon");
 $date=&Date_ConvTZ($date,"PST","CST");

Both timezones MUST be in one of the formst listed below in the section TIMEZONES.

Date_Init
 $flag=&Date_Init();
 $flag=&Date_Init("VAR=VAL","VAR=VAL",...);

Normally, it is not necessary to explicitely call Date_Init. The first time any of the other routines are called, Date_Init will be called to set everything up. If for some reason you want to change the configuration of Date::Manip, you can pass the appropriate string or strings into Date_Init to reinitizize things.

The strings to pass in are of the form ``VAR=VAL''. Any number may be included and they can come in any order. VAR may be any configuration variable. A list of all configuaration variables is given in the section CUSTOMIZING DATE::MANIP below. VAL is any allowed value for that variable. For example, to switch from English to French and use non-US format (so that 12/10 is Oct 12), do the following:

  &Date_Init("Language=French","DateFormat=nonUS");

Note that the usage of Date_Init changed with version 5.07. The old calling convention is allowed but is depreciated.

If you change timezones in the middle of using Date::Manip, comparing dates from before the switch to dates from after the switch will produce incorrect results.

Date_IsWorkDay
  $flag=&Date_IsWorkDay($date [,$flag]);

This returns 1 if $date is a work day. If $flag is non-zero, the time is checked to see if it falls within work hours.

Date_NextWorkDay
  $date=&Date_NextWorkDay($date,$off [,$time]);

Finds the day $off work days from now. If $time is passed in, we must also take into account the time of day.

If $time is not passed in, day 0 is today (if today is a workday) or the next work day if it isn't. In any case, the time of day is unaffected.

If $time is passed in, day 0 is now (if now is part of a workday) or the start of the very next work day.

Date_PrevWorkDay
  $date=&Date_PrevWorkDay($date,$off [,$time]);

Similar to Date_NextWorkDay.

Date_NearestWorkDay
  $date=&Date_NearestWorkDay($date [,$tomorrowfirst]);

This looks for the work day nearest to $date. If $date is a work day, it is returned. Otherwise, it will look forward or backwards in time 1 day at a time until a work day is found. If $tomorrowfirst is non-zero (or if it is omitted and the config variable TomorrowFirst is non-zero), we look to the future first. Otherwise, we look in the past first. In otherwords, in a normal week, if $date is Wednesday, $date is returned. If $date is Saturday, Friday is returned. If $date is Sunday, Monday is returned. If Wednesday is a holiday, Thursday is returned if $tomorrowfirst is non-nil or Tuesday otherwise.

DateManipVersion
  $version=&DateManipVersion

Returns the version of Date::Manip.


TIMEZONES

The following timezone names are currently understood (and can be used in parsing dates). These are zones defined in RFC 822.

    Universal:  GMT, UT
    US zones :  EST, EDT, CST, CDT, MST, MDT, PST, PDT
    Military :  A to Z (except J)
    Other    :  +HHMM or -HHMM
    ISO 8601 :  +HH:MM, +HH, -HH:MM, -HH

In addition, the following timezone abbreviations are also accepted. In a few cases, the same abbreviation is used for two different timezones (for example, NST stands for Newfoundland Standare -0330 and North Sumatra +0630). In these cases, only 1 of the two is available. The one preceded by a ``#'' sign is NOT available but is documented here for completeness. This list of zones comes from the Time::Zone module by Graham Barr, David Muir Sharnoff, and Paul Foley (with some additions by myself).

      IDLW    -1200    International Date Line West
      NT      -1100    Nome
      HST     -1000    Hawaii Standard
      CAT     -1000    Central Alaska
      AHST    -1000    Alaska-Hawaii Standard
      YST     -0900    Yukon Standard
      HDT     -0900    Hawaii Daylight
      YDT     -0800    Yukon Daylight
      PST     -0800    Pacific Standard
      PDT     -0700    Pacific Daylight
      MST     -0700    Mountain Standard
      MDT     -0600    Mountain Daylight
      CST     -0600    Central Standard
      CDT     -0500    Central Daylight
      EST     -0500    Eastern Standard
      EDT     -0400    Eastern Daylight
      AST     -0400    Atlantic Standard
     #NST     -0330    Newfoundland Standard       nst=North Sumatra    +0630
      NFT     -0330    Newfoundland
     #GST     -0300    Greenland Standard          gst=Guam Standard    +1000
     #BST     -0300    Brazil Standard             bst=British Summer   +0100
      ADT     -0300    Atlantic Daylight
      NDT     -0230    Newfoundland Daylight
      AT      -0200    Azores
      WAT     -0100    West Africa
      GMT     +0000    Greenwich Mean
      UT      +0000    Universal (Coordinated)
      UTC     +0000    Universal (Coordinated)
      WET     +0000    Western European
      CET     +0100    Central European
      FWT     +0100    French Winter
      MET     +0100    Middle European
      MEWT    +0100    Middle European Winter
      SWT     +0100    Swedish Winter
      BST     +0100    British Summer              bst=Brazil standard  -0300
      GB      +0100    GMT with daylight savings
      CEST    +0200    Central European Summer
      EET     +0200    Eastern Europe, USSR Zone 1
      FST     +0200    French Summer
      MEST    +0200    Middle European Summer
      METDST  +0200    An alias for MEST used by HP-UX
      SST     +0200    Swedish Summer              sst=South Sumatra    +0700
      EEST    +0300    Eastern Europe Summer
      BT      +0300    Baghdad, USSR Zone 2
      IT      +0330    Iran
      ZP4     +0400    USSR Zone 3
      ZP5     +0500    USSR Zone 4
      IST     +0530    Indian Standard
      ZP6     +0600    USSR Zone 5
      NST     +0630    North Sumatra               nst=Newfoundland Std -0330
     #SST     +0700    South Sumatra, USSR Zone 6  sst=Swedish Summer   +0200
      CCT     +0800    China Coast, USSR Zone 7
      AWST    +0800    West Australian Standard
      WST     +0800    West Australian Standard
      JST     +0900    Japan Standard, USSR Zone 8
      ROK     +0900    Republic of Korea
      CAST    +0930    Central Australian Standard
      EAST    +1000    Eastern Australian Standard
      GST     +1000    Guam Standard, USSR Zone 9  gst=Greenland Std    -0300
      CADT    +1030    Central Australian Daylight
      EADT    +1100    Eastern Australian Daylight
      IDLE    +1200    International Date Line East
      NZST    +1200    New Zealand Standard
      NZT     +1200    New Zealand
      NZDT    +1300    New Zealand Daylight

Others can be added in the future upon request.

DateManip needs to be able to determine the local timezone. It can do this by certain things such as the TZ environment variable (see Date_TimeZone documentation above) or useing the TZ config variable (described below). In either case, the timezone can be of the form STD#DST (for example EST5EDT). Both the standard and daylight savings time abbreviations must be in the table above in order for this to work. Also, this form may NOT be used when parsing a date as there is no way to determine whether the date is in daylight saving time or not. The following forms are also available and are treated similar to the STD#DST forms:

      US/Pacific
      US/Mountain
      US/Central
      US/Eastern


BUSINESS MODE

Anyone using business mode is going to notice a few quirks about it which should be explained. When I designed business mode, I had in mind what UPS tells me when they say 2 day delivery, or what the local business which promises 1 business day turnaround really means.

If you do a business day calculation (with the workday set to 9:00-5:00), you will get the following:

   Saturday at noon + 1 business day = Tuesday at 9:00
   Saturday at noon - 1 business day = Friday at 9:00

What does this mean?

We have a business that works 9-5 and they have a drop box so I can drop things off over the weekend and they promise 1 business day turnaround. If I drop something off Friday night, Saturday, or Sunday, it doesn't matter. They're going to get started on it Monday morning. It'll be 1 business day to finish the job, so the earliest I can expect it to be done is around 17:00 Monday or 9:00 Tuesday morning. Unfortunately, there is some ambiguity as to what day 17:00 really falls on, similar to the ambiguity that occurs when you ask what day midnight falls on. Although it's not the only answer, Date::Manip treats midnight as the beginning of a day rather than the end of one. In the same way, 17:00 is equivalent to 9:00 the next day and any time the date calculations encounter 17:00, it automatically switch to 9:00 the next day. Although this introduces some quirks, I think this is justified. You just have to treat 9:00 as being ambiguous (in the same way you treat midnight as being ambiguous).

Equivalently, if I want a job to be finished on Saturday (despite the fact that I cannot pick it up since the business is closed), I have to drop it off no later than Friday at 9:00. That gives them a full business day to finish it off. Of course, I could just as easily drop it off at 17:00 Thursday, or any time between then and 9:00 Friday. Again, it's a matter of treating 9:00 as ambiguous.

So, in case the business date calculations ever produce results that you find confusing, I believe the solution is to write a wrapper which, whenever it sees a date with the time of exactly 9:00, it treats it specially (depending on what you want.

So Saturday + 1 business day = Tuesday at 9:00 (which means anything from Monday 17:00 to Tuesday 9:00), but Monday at 9:01 + 1 business day = Tuesday at 9:01 which is exact.

If this is not exactly what you have in mind, don't use the DateCalc routine. You can probably get whatever behavior you want using the routines Date_IsWorkDay, Date_NextWorkDay, and Date_PrevWorkDay described above.


CUSTOMIZING DATE::MANIP

There are a number of variables which can be used to customize the way Date::Manip behaves. There are also several ways to set these variables.

At the top of the Manip.pm file, there is a section which contains all customization variables. These provide the default values.

These can be overridden in a global config file if one is present (this file is optional). If the GlobalCnf variable is set in the Manip.pm file, it contains the full path to a config file. If the file exists, it's values will override those set in the Manip.pm file. A sample config file is included with the Date::Manip distribution. Modify it as appropriate and copy it to some appropriate directory and set the GlobalCnf variable in the Manip.pm file.

Each user can have a personal config file which is of the same form as the global config file. The variables PersonalCnf and PersonalCnfPath set the name and search path for the personal config file. This file is also optional.

NOTE: if you use business mode calculations, you must have a config file (either global or personal) since this is the only place where you can define holidays.

Finally, any variables passed in through Date_Init override all other values.

A config file can be composed of several sections (though only 2 of them are currently used). The first section sets configuration varibles. Lines in this section are of the form:

   VARIABLE = VALUE

For example, to make the default language French, include the line:

   Language = French

Only variables described below may be used. Blank lines and lines beginning with a pound sign (#) are ignored. All spaces are optional and strings are case insensitive.

A line which starts with an asterix (*) designates a new section. The only section currently used is the Holiday section. All lines are of the form:

   DATE = HOLIDAY

HOLIDAY is the name of the holiday (or it can be blank in which case the day will still be treated as a holiday... for example the day after Thanksgiving or Christmas is often a work holiday though neither are named).

DATE is a string which can be parsed to give a valid date in any year. It can be of the form

   Date
   Date + Delta
   Date - Delta

A valid holiday section would be:

   *Holiday
   1/1                             = New Year's Day
   third Monday in Feb             = Presidents' Day
   fourth Thu in Nov               = Thanksgiving
   # The Friday after Thanksgiving is an unnamed holiday most places
   fourth Thu in Nov + 1 day       =

In a Date + Delta or Date - Delta string, you can use business mode by including the appropriate string (see documentation on DateCalc) in the Date or Delta. So (in English), the first workday before Christmas could be defined as:

   12/25 - 1 business day          =

All Date::Manip variables which can be used are described in the following section.

IgnoreGlobalCnf
If this variable is used (any value is ignored), the global config file is not read. It must be present in the initial call to Date_Init or the global config file will be read.

EraseHolidays
If this variable is used (any value is ignored), the current list of defined holidays is erased. A new set will be set the next time a config file is read in. This can be set in either the global config file or as a Date_Init argument (in which case holidays can be read in from both the global and personal config files) or in the personal config file (in which case, only holidays in the personal config file are counted).

PersonalCnf
This variable can be passed into Date_Init to read a different personal configuration file. It can also be included in the global config file to define where personal config files live.

The default name for the config file is .DateManip.cnf on all Unix platforms and Manip.cnf on all non-Unix platforms (because some of them insist on 8.3 character filenames :-).

PersonalCnfPath
Used in the same way as the PersonalCnf option. You can use tilde (~) expansions when defining the path for Unix and VMS platforms.

Language
Date::Manip can be used to parse dates in many different languages. Currently, it is configured to read English, Swedish, and French dates, but others can be added easily. Language is set to the language used to parse dates.

DateFormat
Different countries look at the date 12/10/96 as Dec 10 or Oct 12. In the United States, the first is most common, but this certainly doesn't hold true for other countries. Setting DateFormat to ``US'' forces the first behavior (Dec 10). Setting DateFormat to anything else forces the second behavior (Oct 12).

TZ
Date::Manip is able to understand some timezones (and others will be added in the future). At the very least, all zones defined in RFC 822 are supported. Currently supported zones are listed in the TIMEZONES section above and all timezones should be entered as one of them.

Date::Manip must be able to determine the timezone the user is in. It does this by looking in the following places:

   the environment variable TZ
   the variable $main::TZ
   the file /etc/TIMEZONE
   the 5th element of the unix "date" command (not available on NT machines)

At least one of these should contain a timezone in one of the supported forms. If it doesn't, the TZ variable must be set to contain the local timezone in the appropriate form.

The TZ variable will override the other methods of determining the timezone, so it should probably be left blank if any of the other methods will work. Otherwise, you will have to modify the variable every time you switch to/from daylight savings time.

ConvTZ
All date comparisons and calculations must be done in a single time zone in order for them to work correctly. So, when a date is parsed, it should be converted to a specific timezone. This allows dates to easily be compared and manipulated as if they are all in a single timezone.

The ConvTZ variable determines which timezone should be used to store dates in. If it is left blank, all dates are converted to the local timezone (see the TZ variable above). If it is set to one of the timezones listed above, all dates are converted to this timezone. Finally, if it is set to the string ``IGNORE'', all timezone information is ignored as the dates are read in (in this case, the two dates ``1/1/96 12:00 GMT'' and ``1/1/96 12:00 EST'' would be treated as identical).

Internal
When a date is parsed using ParseDate, that date is stored in an internal format which is understood by the Date::Manip routines UnixDate and DateCalc. Originally, the format used to store the date internally was:
   YYYYMMDDHH:MN:SS

It has been suggested that I remove the colons (:) to shorten this to:

   YYYYMMDDHHMNSS

The main advantage of this is that some databases are colon delimited which makes storing a date from Date::Manip tedious.

In order to maintain backwards compatibility, the Internal variable was introduced. Set it to 0 (to use the old format) or 1 (to use the new format).

FirstDay
It is sometimes necessary to know what day of week is regarded as first. By default, this is set to Monday, but many countries and people will prefer Sunday (and in a few cases, a different day may be desired). Set the FirstDay variable to be the first day of the week (1=Monday, 7=Sunday) Monday should be chosen to to comply with ISO 8601.

WorkWeekBeg, WorkWeekEnd
The first and last days of the work week. By default, monday and friday. WorkWeekBeg must come before WorkWeekEnd numerically. The days are numbered from 0 (sunday) to 6 (saturday). There is no way to handle an odd work week of Thu to Mon for example.

WorkDay24Hr
If this is non-nil, a work day is treated as being 24 hours long. The WorkDayBeg and WorkDayEnd variables are ignored in this case.

WorkDayBeg, WorkDayEnd
The times when the work day starts and ends. WorkDayBeg must come before WorkDayEnd (i.e. there is no way to handle the night shift where the work day starts one day and ends another). Also, the workday MUST be more than one hour long (of course, if this isn't the case, let me know... I want a job there!).

The time in both can be in any valid time format (including international formats), but seconds will be ignored.

TomorrowFirst
Periodically, if a day is not a business day, we need to find the nearest business day to it. By default, we'll look to ``tomorrow'' first, but if this variable is set to 0, we'll look to ``yesterday'' first. This is only used in the Date_NearestWorkDay and is easily overridden (see documentation for that function).

DeltaSigns
Prior to Date::Manip version 5.07, a negative delta would put negative signs in front of every component (i.e. ``0:0:-1:-3:0:-4''). By default, 5.07 changes this behavior to print only 1 or two signs in front of the year and day elements (even if these elements might be zero) and the sign for year/month and day/hour/minute/second are the same. Setting this variable to non-zero forces deltas to be stored with a sign in front of every element (including elements equal to 0).

Jan1Week1
ISO 8601 states that the first week of the year is the one which contains Jan 4 (i.e. it is the first week in which most of the days in that week fall in that year). This means that the first 3 days of the year may be treated as belonging to the last week of the previous year. If this is set to non-nil, the ISO 8601 standard will be ignored and the first week of the year contains Jan 1.

YYtoYYYY
By default, a 2 digit year is treated as falling in the 100 year period of CURR-89 to CURR+10. YYtoYYYY may be set to any integer N to force a 2 digit year into the period CURR-N to CURR+(99-N). A value of 0 forces the year to be the current year or later. A value of 99 forces the year to be the current year or earlier. Since I do no checking on the value of YYtoYYYY, you can actually have it any positive or negative value to force it into any century you want.

YYtoYYYY can also be set to ``C'' to force it into the current century, or to ``C##'' to force it into a specific century. So, no (1998), ``C'' forces 2 digit years to be 1900-1999 and ``C18'' would force it to be 1800-1899.

It can also be set to the form ``C####'' to force it into a specific 100 year period. C1950 refers to 1950-2049.

UpdateCurrTZ
If a script is running over a long period of time, the timezone may change during the course of running it (i.e. when daylight savings time starts or ends). As a result, parsing dates may start putting them in the wrong time zone. Since a lot of overhead can be saved if we don't have to check the current timezone every time a date is parsed, by default checking is turned off. Setting this to non-nill will force timezone checking to be done every time a date is parsed... but this will result in a considerable performance penalty.

A better solution would be to restart the process on the two days per year where the timezone switch occurs.

IntCharSet
If set to 0, use the US character set (7-bit ASCII) to return strings such as the month name. If set to 1, use the appropriate international character set.

ForceDate
This variable can be set to a date in the format: YYYY-MM-DD-HH:MN:SS to force the current date to be interpreted as this date. Since the current date is used in parsing, this string will not be parsed and MUST be in the format given above.


BACKWARDS INCOMPATIBILITIES

For the most part, Date::Manip has remained backward compatible at every release. There have been a few minor incompatibilities introduced at various stages. Major differences are marked with bullets.

VERSION 5.32
Date_Init arguments
The old style Date_Init arguments that were deprecated in version 5.07 have been removed.

  • DateManip.cnf change
    Changed .DateManip.cnf to Manip.cnf (to get rid of problems on OS's that insist on 8.3 filenames) for all non-Unix platforms (Wintel, VMS, Mac). For all Unix platforms, it's still .DateManip.cnf . It will only look in the user's home directory on VMS and Unix.

  • VERSION 5.30
    • Delta format changed
      A week field has been added to the internal format of the delta. It now reads ``Y:M:W:D:H:MN:S'' instead of ``Y:M:D:H:MN:S''.

    VERSION 5.21
    Long running processes may give incorrect timezone
    A process that runs during a timezone change (Daylight Saving Time specifically) may report the wrong timezone. See the UpdateCurrTZ variable for more information.

    UnixDate ``%J'', ``%W'', and ``%U'' formats fixed
    The %J, %W, and %U will no longer report a week 0 or a week 53 if it should really be week 1 of the following year. They now report the correct week number according to ISO 8601.

    VERSION 5.20
    • ParseDate formats removed (ISO 8601 compatibility)
      Full support for ISO 8601 formats was added. As a result, some formats which previously worked may no longer be parsed since they conflict with an ISO 8601 format. These include MM-DD-YY (conflicts with YY-MM-DD) and YYMMDD (conflicts with YYYYMM). MM/DD/YY still works, so the first form can be kept easily by changing ``-'' to ``/''. YYMMDD can be changed to YY-MM-DD before being parsed. Whenever parsing dates using dashes as separators, they will be treated as ISO 8601 dates. You can get around this by converting all dashes to slashes.

    • Week day numbering
      The day numbering was changed from 0-6 (sun-sat) to 1-7 (mon-sun) to be ISO 8601 compatible. Weeks start on Monday (though this can be overridden using the FirstDay config variable) and the 1st week of the year contains Jan 4 (though it can be forced to contain Jan 1 with the Jan1Week1 config variable).

    VERSION 5.07
    UnixDate ``%s'' format
    Used to return the number of seconds since 1/1/1970 in the current timezone. It now returns the number of seconds since 1/1/1970 GMT. The ``%o'' format was added which returns what ``%s'' previously did.

    Internal format of delta
    The format for the deltas returned by ParseDateDelta changed. Previously, each element of a delta had a sign attached to it (+1:+2:+3:+4:+5:+6). The new format removes all unnecessary signs by default (+1:2:3:4:5:6). Also, because of the way deltas are normalized (see documentation on ParseDateDelta), at most two signs are included. For backwards compatibility, the config variable DeltaSigns was added. If set to 1, all deltas include all 6 signs.

    Date_Init arguments
    The format of the Date_Init calling arguments changed. The old method
      &Date_Init($language,$format,$tz,$convtz);

    is still supported , but this support will likely disappear in the future. Use the new calling format instead:

      &Date_Init("var=val","var=val",...);

    NOTE: The old format is no longer supported as of version 5.32 .


    KNOWN PROBLEMS

    The following are not bugs, but they may give some people problems.

    Unable to determine TimeZone
    Perhaps the most common problem occurs when you get the error:
       Error: Date::Manip unable to determine TimeZone.

    Date::Manip tries hard to determine the local timezone, but on some machines, it cannot do this (especially non-unix systems). To fix this, just set the TZ variable, either at the top of the Manip.pm file, or in the DateManip.cnf file. I suggest using the form ``EST5EDT'' so you don't have to change it every 6 months when going to or from daylight savings time.

    A minor (false) assumption that some users might make is that since Date::Manip passed all of it's tests at install time, this should not occur and are surprised when it does.

    Some of the tests are timezone dependent. Since the tests all include input and expected output, I needed to know in advance what timezone they would be run in. So, the tests all explicitely set the timezone using the TZ configuration variable passed into Date_Init. Since this overrides any other method of determining the timezone, Date::Manip uses this and doesn't have to look elsewhere for the timezone.

    When running outside the tests, Date::Manip has to rely on it's other methods for determining the timezone.

    Complaining about getpwnam/getpwuid
    Another problem is when running on Micro$oft OS'es. I have added many tests to catch them, but they still slip through occasionally. If any ever complain about getpwnam/getpwuid, simply add one of the lines:
      $ENV{OS} = Windows_NT
      $ENV{OS} = Windows_95

    to your script before

      use Date::Manip

    Date::Manip is slow
    The reasons for this are covered in the SHOULD I USE DATE::MANIP section above.

    Some things that will definitely help:

    Version 5.21 does run noticably faster than earlier versions due to rethinking some of the initialization, so at the very least, make sure you are running this version or later.

    ISO-8601 dates are parsed first and fastest. Use them whenever possible.

    Avoid parsing dates that are referenced against the current time (in 2 days, today at noon, etc.). These take a lot longer to parse.

       Example:  parsing 1065 dates with version 5.11 took 48.6 seconds, 36.2
       seconds with version 5.21, and parsing 1065 ISO-8601 dates with version
       5.21 took 29.1 seconds (these were run on a slow, overloaded computer with
       little memory... but the ratios should be reliable on a faster computer).

    Business date calculations are extremely slow. You should consider alternatives if possible (i.e. doing the calculation in exact mode and then multiplying by 5/7). There will be an approximate business mode in one of the next versions which will be much faster (though less accurate) which will do something like this. Whenever possible, use this mode. And who needs a business date more accurate than ``6 to 8 weeks'' anyway huh :-)

    Never call Date_Init more than once. Unless you're doing something very strange, there should never be a reason to anyway.

    Sorting Problems
    If you use Date::Manip to sort a number of dates, you must call Date_Init either explicitely, or by way of some other Date::Manip routine before it is used in the sort. For example, the following code fails:
       use Date::Manip;
       # &Date_Init;
       sub sortDate {
           my($date1, $date2);
           $date1 = &ParseDate($a);
           $date2 = &ParseDate($b);
           return ($date1 cmp $date2);
       }
       @date = ("Fri 16 Aug 96",
                "Mon 19 Aug 96",
                "Thu 15 Aug 96");
       @i=sort sortDate @dates;

    but if you uncomment the Date_Init line, it works. The reason for this is that the first time you call Date_Init, it initializes a number of items used by Date::Manip. Some of these have to be sorted (regular expressions sorted by length to ensure the longest match). It turns out that perl (5.004 and earlier) has a bug in it which does not allow a sort within a sort. At some point, this should be fixed, but for now, the best thing to do is to call Date_Init explicitely.

    NOTE: This is an EXTREMELY inefficient way to sort data. Instead, you should parse the dates with ParseDate, sort them using a normal string comparison, and then convert them back to the format desired using UnixDate.

    RCS Control
    If you try to put Date::Manip under RCS control, you are going to have problems. Apparently, RCS replaces strings of the form ``$Date...$'' with the current date. This form occurs all over in Date::Manip. To prevent the RCS keyword expansion, checkout files using ``co -ko''. Since very few people will ever have a desire to do this (and I don't use RCS), I have not worried about it.


    KNOWN BUGS

    Daylight Savings Times
    Date::Manip does not handle daylight savings time, though it does handle timezones to a certain extent. Converting from EST to PST works fine. Going from EST to PDT is unreliable.

    The following examples are run in the winter of the US East coast (i.e. in the EST timezone).

            print UnixDate(ParseDate("6/1/97 noon"),"%u"),"\n";
            => Sun Jun  1 12:00:00 EST 1997

    June 1 EST does not exist. June 1st is during EDT. It should print:

            => Sun Jun  1 00:00:00 EDT 1997

    Even explicitely adding the timezone doesn't fix things (if anything, it makes them worse):

            print UnixDate(ParseDate("6/1/97 noon EDT"),"%u"),"\n";
            => Sun Jun  1 11:00:00 EST 1997

    Date::Manip converts everything to the current timezone (EST in this case).

    Related problems occur when trying to do date calculations over a timezone change. These calculations may be off by an hour.

    Also, if you are running a script which uses Date::Manip over a period of time which starts in one time zone and ends in another (i.e. it switches form Daylight Savings Time to Standard Time or vice versa), many things may be wrong (especially elapsed time).

    I hope to fix these problems in a future release so that it would convert everything to the current zones (EST or EDT).


    BUGS AND QUESTIONS

    If you find a bug in Date::Manip, please send it directly to me (see the AUTHOR section below) rather than posting it to one of the newsgroups. Although I try to keep up with the comp.lang.perl.* groups, all too often I miss news (flaky news server, articles expiring before I caught them, 1200 articles to wade through and I missed one that I was interested in, etc.).

    If you have a problem using Date::Manip that perhaps isn't a bug (can't figure out the syntax, etc.), you're in the right place. Go right back to the top of this man page and start reading. If this still doesn't answer your question, mail me (again, please mail me rather than post to the newsgroup).


    YEAR 2000

    In hindsight, the fact that I've only been asked once (so far) if Date::Manip is year 2000 compliant surprises me a bit. Still, as 2000 approaches and this buzzword starts flying around more and more frantically, other's might follow suit, so this section answers the question.

    Is Date::Manip year 2000 compliant? Yes, but the question is largely unmeaningful. Date::Manip is basically a parser. It'll parse dates in any of thousands of different formats (including the 2 digit years that are going to cause the computer equivalent of doomsday on Dec 31, 1999). But, internally, Date::Manip stores years as 4 digits, and all of it's functions work with the 4 digit representation, so there is no problem with dates after 2000.

    The better question is ``Is Perl year 2000 compliant''? This is such a good question, that it's in the perl FAQ. Go read ``Does Perl have a year 2000 problem'' in section 4.

    The best question is ``For what dates is Date::Manip useful?'' It definitely can't handle BC dates, or dates past Dec 31, 9999. Also, one of the basic routines I wrote counts the days since Dec 31, 0999. I realize now that I should have had it calculate days since Dec 31, 0001 BC, but I didn't. One day I may go back and change this, but until I do, dates in the first millenium (0001 to 0999) probably won't work. So, I guarantee that Date::Manip works during the years 1000 to 9999.

    In practical terms however, Date::Manip deals with the Gregorian calendar, and is therefore useful in the period that that calendar has been, or will be, in effect. The Gregorian calendar was first adopted by the Catholic church in 1582, but some countries were still using the Julian calendar as late as the early part of this century. Also, at some point around the year 3000, the calendar system is going to have to be modified slightly since the current system of leap years will be off by one day every 3200 years or so. So... in practical terms, Date::Manip is _probably_ useful from 1900 to 3000. Approximately.

    One other note is that Date::Manip will NOT handle 3 digit years. So, if you store the year as an offset from 1900 (which is 2 digits now, but will become 3 digits in 2000), these will NOT be parsable by Date::Manip.

    Finally, Date::Manip is flexible. It will allow you to write Year 2000 NON-compliant code if you really want to.


    ACKNOWLEDGEMENTS

    There are many people who have contributed to Date::Manip over the years that I'd like to thank. The most important contributions have come in the form of suggestions and bug reports by users. I have tried to include the name of every person who first suggested each improvement or first reported each bug. These are included in the HISTORY file in the Date::Manip distribution. The list is simply too long to appear here, but I appreciate their help.

    I'd also like a couple of authors. Date::Manip has recently been getting some really good press in a couple of books. Since no one's paying me to write Date::Manip, seeing my module praised in a book written by someone else is really great. My thanks to Nate Patwardhan and Clay Irving (Programming with Perl Modules -- part of the O'Reilly Perl Resource Kit); and Tom Christiansen and Nathan Torkington (for the forthcoming book The Perl Cookbook). Also, thanks to any other authors who've written about Date::Manip who's books I haven't seen.


    AUTHOR

    Sullivan Beck (sbeck@cise.ufl.edu)

    You can always get the newest beta version of Date::Manip (which may fix problems in the current CPAN version... and may add others) from my home page:

    http://www.cise.ufl.edu/~sbeck/

     Date::Manip - date manipulation routines