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Date::Manip::Changes5to6(3)    User Contributed Perl Documentation    Date::Manip::Changes5to6(3)

NAME
       Date::Manip::Changes5to6 - describes differences between 5.xx and 6.00

SYNOPSIS
       Date::Manip 6.00 represents a complete rethink and rewrite of Date::Manip.  A great deal
       of effort was made to make sure that 6.00 is almost backwards compatible with 5.xx
       whenever feasible, but some functionality has changed in backwards incompatible ways.
       Other parts have been deprecated and will be removed at some point in the future.

       This document describes the differences between the 5.xx series and version 6.00. This
       page primarily describes technical details, most of which do not impact how Date::Manip is
       used in scripts. If you want to make sure that a script which ran with 5.xx will run with
       6.xx, refer to the Date::Manip::Migration5to6 document.

OVERVIEW
       The Date::Manip 5.xx series of suffered from several weaknesses. These included:

       Poor time zone support
	   Time zone support in 5.xx was broken. Determining a time zone, and understanding
	   daylight saving time changes was incomplete (at best) and totally inadequate to do
	   true timezone operations.

       Parsing too complicated and unstructured
	   The parsing routines had grown very complicated, and overly permissive over time and
	   were in need of a complete overhaul.

       Lacking OO model
	   Date::Manip 5.xx was written as a functional module, not an OO module, but date
	   handling would lend itself very well to being OO with different classes to handle
	   dates, deltas, and recurrences.

	   The OO model allows a lot of information to be stored with each date (such as time
	   zone information) which is discarded in the functional interface.

       Too monolithic
	   The entire Date::Manip module was contained in one huge file. Breaking up the module
	   would make it much easier to deal with.

       Date::Manip 6.00 is a complete rewrite of Date::Manip to address these and other issues.

       The following sections address how Date::Manip 6.00 differs from previous releases, and
       describes changes that might need to be made to your script in order to upgrade from 5.xx
       to 6.00.

       The most important changes are marked with asterisks.

GENERAL CHANGES
       (*) Requires perl 5.10.0
	   Please see the Date::Manip::Problems document for a discussion of this problem. It's
	   in the KNOWN COMPLAINTS section.

       (*) Breaking into smaller modules
	   Date::Manip module has been broken up from one huge module into a large number of
	   smaller more manageable modules. The main Date::Manip module is still present, and
	   contains all of the functions from Date::Manip 5.xx (except that they now call
	   functions from all the other modules to do the actual work). In general, the
	   Date::Manip module from 6.00 is backwards compatible.

	   A number of new modules have been created as well. These can be used directly,
	   bypassing the main Date::Manip module. These include the following:

	   Date::Manip::Base contains many basic date operations which may be used to do simple
	   date manipulation tasks without all the overhead of the full Date::Manip module.

	   Date::Manip::TZ contains time zone operations.

	   Handling dates, deltas, and recurrences are now done in Date::Manip::Date,
	   Date::Manip::Delta, and Date::Manip::Recur.

	   All of these modules are object oriented, and are designed to be used directly, so if
	   you prefer an OO interface over a functional interface, use these modules.

       (*) Intermediate data cached
	   In order to improve the performance of Date::Manip, many intermediate values are
	   cached. This does impact the memory footprint of the module, but it has a huge impact
	   on the performance of the module.

	   Some types of data depend on the config variables used, and these are cached
	   separately, and this cache is automatically cleared every time a config variable is
	   set. As a result, it is best if you set all config variables at the start, and then
	   leave them alone completely to get optimal use of cached data.

	   A side effect of all this is that the Memoize module should not be used in conjunction
	   with Date::Manip.

	   In the version 5.xx documentation, it was mentioned that the Memoize module might be
	   used to improve performance in some cases. This is no longer the case. It should not
	   be used with Date::Manip, even if you use the functional interface instead of the OO
	   interface.

       Taint safe
	   Date::Manip now contains no tainted data, and should run without problems with taint
	   checking on provided you do not set additional methods for determining the system time
	   zone using the curr_zone_methods function.

	   Ideally, this should never be necessary. If it is necessary, I'd like to hear about it
	   so that I can add whatever standard methods are needed to the built in list.

TIME ZONE SUPPORT
       (*) Complete handling of time zones
	   The biggest problem with Date::Manip 5.xx was it's inability to correctly handle time
	   zones and Daylight Saving Time. That is now fixed. Version 6.00 includes support for
	   every time zone included in the zoneinfo (aka Olson) database which includes the
	   definitions of (hopefully) all of the time zones used in the world.

       Individual time zones will no longer be added
	   Prior to 5.55, time zones were added upon request. Since 6.00 now supports a full set
	   of standard time zones, I will no longer add in individual time zones (Date::Manip::TZ
	   includes functionality for adding them yourself if they are needed).  With Date::Manip
	   now having full time zone support, I'm not interested in supporting my own time zone
	   database.

	   However, I am interested in adding sets of time zones from various "standards".

	   Date::Manip 6.00 includes time zones from the following standards:

	      Olson zoneinfo database
	      all Microsoft Windows time zones
	      zones listed in RFC-822

	   If there are additional standards that include additional time zones not included
	   here, please point me to them so they can be added.	This could include published
	   lists of time zone names supported on some operating system which have different names
	   than the zoneinfo list.

       Nonstandard time zone abbreviations removed
	   Some of the individual standards that were added in the 5.xx series are not included
	   in any of the standards listed above.

	   As of 6.00, only time zones from standards will be included in the distribution
	   (others can be added by users using the functions described in Date::Manip::TZ to add
	   aliases for existing time zones).

	   The following time zones were in Date::Manip 5.xx but not in 6.00.

	      IDLW    -1200    International Date Line West
	      NT      -1100    Nome
	      SAT     -0400    Chile
	      CLDT    -0300    Chile Daylight
	      AT      -0200    Azores
	      MEWT    +0100    Middle European Winter
	      MEZ     +0100    Middle European
	      FWT     +0100    French Winter
	      GB      +0100    GMT with daylight saving
	      SWT     +0100    Swedish Winter
	      MESZ    +0200    Middle European Summer
	      FST     +0200    French Summer
	      METDST  +0200    An alias for MEST used by HP-UX
	      EETDST  +0300    An alias for eest used by HP-UX
	      EETEDT  +0300    Eastern Europe, USSR Zone 1
	      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
	      AWST    +0800    Australian Western Standard
	      ROK     +0900    Republic of Korea
	      AEST    +1000    Australian Eastern Standard
	      ACDT    +1030    Australian Central Daylight
	      CADT    +1030    Central Australian Daylight
	      AEDT    +1100    Australian Eastern Daylight
	      EADT    +1100    Eastern Australian Daylight
	      NZT     +1200    New Zealand
	      IDLE    +1200    International Date Line East

       A lot of support modules and files
	   Date::Manip now includes a large number of files and modules that are used to support
	   time zones.

	   A series of modules are included which are auto-generated from the zoneinfo database.
	   The Date::Manip::Zones, Date::Manip::TZ::*, and Date::Manip::Offset::* modules are all
	   automatically generated and are not intended to be used directly. Instead, the
	   Date::Manip::TZ module is used to access the data stored there.

	   A separate time zone module (Date::Manip::TZ::*) is included for every single time
	   zone. There is also a module (Date::Manip::Offset::*) for every different offset. All
	   told, there are almost 1000 modules.  These are included to make time zone handling
	   more efficient. Rather than calculating everything on the fly, information about each
	   time zone and offset are included here which greatly speeds up the handling of time
	   zones. These modules are only loaded as needed (i.e. only the modules related to the
	   specific time zones you refer to are ever loaded), so there is no performance penalty
	   to having them.

	   Also included in the distribution are a script (tzdata) and additional module
	   (Date::Manip::TZdata). These are used to automatically generate the time zone modules,
	   and are of no use to anyone other than the maintainer of Date::Manip. They are
	   included solely for the sake of completeness. If someone wanted to fork Date::Manip,
	   all the tools necessary to do so are included in the distribution.

       (*) Meaning of $::TZ and $ENV{TZ}
	   In Date::Manip 5.x, you could specify what time zone you wanted to work in using
	   either the $::TZ or $ENV{TZ} variables.

	   Date::Manip 6.00 makes use of two different time zones: the actual local time zone the
	   computer is running in (and which is used by the system clock), and a time zone that
	   you want to work in. Typically, these are the same, but they do not have to be.

	   As of Date::Manip 6.00, the $::TZ and $ENV{TZ} variables are used only to specify the
	   actual local time zone.

	   In order to specify an alternate time zone to work in, use the SetDate or ForceDate
	   config variables.

CONFIG FILES AND VARIABLES
       (*) Date_Init handling of config variables
	   The handling of config variables has changed slightly.

	   Previously, variables passed in to Date_Init overrode values from config files. This
	   has changed slightly. Options to Date_Init are now parsed in the order they are
	   listed, so the following:

	      Date_Init("DateFormat=Other","ConfigFile=DateManip.cnf")

	   would first set the DateFormat variable, and then it would read the config file
	   "DateManip.cnf". If that config file included a DateFormat definition, it would
	   override the one passed in to Date_Init.

	   The proper way to override config files is to pass the config files in first, followed
	   by any script-specific overrides. In other words:

	      Date_Init("ConfigFile=DateManip.cnf","DateFormat=Other")

       Date_Init doesn't return the config variables
	   In Date::Manip::5.xx, Date_Init could return the list of all config variables. This
	   functionality is no longer supported.  Date_Init is used strictly to set config
	   variables.

       (*) Config file options
	   Date::Manip 5.xx had the concept of a global and personal config file. In addition,
	   the personal config file could be looked for in a path of directories. All this was
	   specified using the config variables:

	      GlobalCnf
	      IgnoreGlobalCnf
	      PersonalCnf
	      PersonalCnfPath
	      PathSep

	   All of these have been removed. Instead, the single config variable:

	      ConfigFile

	   will be used to specify config files (with no distinction between a global and
	   personal config file). Also, no path searching is done. Each must be specified by a
	   complete path. Finally, any number of config files can be used. So the following is
	   valid:

	      Date_Init("ConfigFile=./Manip.cnf","ConfigFile=/tmp/Manip.cnf")

       Other config variables removed
	   The following config variables have been removed.

	      TodayIsMidnight  Use DefaultTime instead.

	      ConvTZ	       Use SetDate or ForceDate instead.

	      Internal	       Use Printable instead.

	      DeltaSigns       Use the Date::Manip::Delta::printf
			       method to print deltas

	      UpdateCurrTZ     With real time zone handling in
			       place, this is no longer necessary

       Other config variables deprecated
	   The following config variables are deprecated and will be removed in some future
	   version:

	      TZ	      Use SetDate or ForceDate instead.

	      IntCharSet      This has been replaced with better support for
			      international character sets. The Encoding config
			      variable may be used instead.

       Holidays
	   Previously, holidays could be defined as a "Date + Delta" or "Date - Delta" string.
	   These predate recurrences, and introduce some complexity into the handling of
	   holidays. Since recurrences are a much better way to define holidays, the "Date +
	   Delta" and "Date - Delta" strings are no longer supported.

       TZ replaced (and enhanced)
	   The SetDate and ForceDate variables (which include the functionality of the deprecated
	   TZ variable) are much improved as described in the Date::Manip::Config documentation.

	   Since it is now handles time change correctly (allowing time changes to occur in the
	   alternate time zone), parsed results may be different than in 5.x (but since 5.x
	   didn't have proper time zone handling, this is a good thing).

DATE PARSING AND OPERATIONS
       (*) today, tomorrow, yesterday
	   The words "today", "tomorrow", and "yesterday" in 5.xx referred to the time now, 24
	   hours in the future, and 24 hours in the past respectively.

	   As of 6.00, these are treated strictly as date strings, so they are the current day,
	   the day before, or the day after at the time 00:00:00.

	   The string "now" still refers to the current date and time.

       ISO 8601 formats
	   A couple of the date formats from Date::Manip 5.xx conflicted with ISO 8601 formats in
	   the spec. These are documented in the Date::Manip::Date documentation.

	   Dates are now parsed according to the spec (though a couple extensions have been made,
	   which are also documented in the Date::Manip::Date documentation).

	   There is one change with respect to Date::Manip 5.xx that results from a possible
	   misinterpretation of the standard. In Date::Manip, there is a small amount of
	   ambiguity in how the Www-D date formats are understood.

	   The date:

	      1996-w02-3

	   might be interpreted in two different ways. It could be interpreted as Wednesday (day
	   3) of the 2nd week of 1996, or as the 3rd day of the 2nd week of 1996 (which would be
	   Tuesday if the week begins on Sunday). Since the specification only works with weeks
	   which begin on day 1, the two are always equivalent in the specification, and the
	   language of the specification doesn't clearly indicate one interpretation over the
	   other.

	   Since Date::Manip supports the concept of weeks starting on days other than day 1
	   (Monday), the two interpretations are not equivalent.

	   In Date::Manip 5.xx, the date was interpreted as Wednesday of the 2nd week, but I now
	   believe that the other interpretation (3rd day of the week) is the interpretation
	   intended by the specification. In addition, if this interpretation is used, it is easy
	   to get the other interpretation.

	   If 1996-w02-3 means the 3rd day of the 2nd week, then to get Wednesday (day 3) of the
	   week, use the following two Date::Manip::Date methods:

	      $err   = $date->parse("1996-w02-1");
	      $date2 = $date->next(3,1);

	   The first call gets the 1st day of the 2nd week, and the second call gets the next
	   Wednesday.

	   If 1996-w02-3 is interpreted as Wednesday of the 2nd week, then to get the 3rd day of
	   the week involves significantly more work.

	   In Date::Manip 6.00, the date will now be parsed as the 3rd day of the 2nd week.

       (*) Parsing is now more rigid
	   The philosophy in Date::Manip 5.xx with respect to parsing dates was "if there's any
	   conceivable way to find a valid date in the string, do so". As a result, strings which
	   did not look like they could contain a valid date often would.

	   This manifested itself it two ways. First, a lot of punctuation was ignored. For
	   example, the string "01 // 03 -. 75" was the date 1975-01-03.

	   Second, a lot of word breaks were optional and it was often acceptable to run strings
	   together. For example, the delta "in5seconds" would have worked.

	   With Date::Manip 6.00, parsing now tries to find a valid date in the string, but uses
	   a more rigidly defined set of allowed formats which should more closely match how the
	   dates would actually be expressed in real life.  The punctuation allowed is more
	   rigidly defined, and word breaks are required. So "01/03/75" will work, but
	   "01//03/75" and "01/03-75" won't. Also, "in5seconds" will no longer work, though "in 5
	   seconds" will work.

	   These changes serve to simplify some of the regular expressions used in parsing dates,
	   as well as simplifying the parsing routines. They also help to recognize actually
	   dates as opposed to typos... it was too easy to pass in garbage and get a date out.

       Support dropped for a few formats
	   I've dropped support for a few very uncommon (probably never used) formats. These
	   include (with Jan 3, 2009 as an example):

	      DD/YYmmm	    03/09Jan
	      DD/YYYYmmm    03/2009Jan
	      mmmYYYY/DD    Jan2009/03
	      YYYY/DDmmm    2009/03Jan

	      mmmYYYY	    Jan2009
	      YYYYmmm	    2009Jan

	   The last two are no longer supported since they are incomplete.

	   With the exception of the incomplete forms, these could be added back in with very
	   little effort. If there is ever a request to do so, I probably will.

       No longer parses the Apache format
	   Date::Manip 5.xx supported the format:

	      DD/mmm/YYYY:HH:MN:SS

	   used in the apache logs. Due to the stricter parsing, this format is no longer
	   supported directly. However, the parse_format method may be used to parse the date
	   directly from an apache log line with no need to extract the date string beforehand.

       Date_PrevWorkDay behavior
	   The behavior of Date_PrevWorkDay has changed slightly.

	   The starting date is checked. If $timecheck was non-zero, the check failed if the date
	   was not a business date, or if the time was not during business hours. If $timecheck
	   was zero, the check failed if the date was not a business date, but the time was
	   ignored.

	   In 5.xx, if the check failed, and $timecheck was non-zero, day 0 was defined as the
	   start of the next business day, but if $timecheck was zero, day 0 was defined as the
	   previous business day at the same time.

	   In 6.x, if the check fails, and $timecheck is non-zero, the behavior is the same as
	   before. If $timecheck is zero, day 0 is defined as the next business day at the same
	   time.

	   So day 0 is now always the same, where before, day 0 meant two different things
	   depending on whether $timecheck was zero or not.

       (*) Default time
	   In Date::Manip 5.xx, the default times for dates was handled in an inconsistent
	   manner.  In the Date::Manip::Date documentation, if you parse a date from the "Common
	   date formats" section, in Date::Manip 5.xx, if no time was included, it defaulted to
	   "00:00:00". If you parsed a date from the "Less common formats" section, the default
	   time was the current time.

	   So running a program on Jun 5, 2009 at noon that parsed the following dates gave the
	   following return values:

	      Jun 12	 =>  Jun 12, 2009 at 00:00:00
	      next week  =>  Jun 12, 2009 at 12:00:00

	   This behavior is changed and now relies on the config variable DefaultTime.	If
	   DefaultTime is "curr", the default time for any date which includes no information
	   about the time is the current time. Otherwise, the default time is midnight.

       %z format
	   In Date::Manip 5.xx, the %z format would give an offset in the form: -0500.	Now it
	   gives it in the form: -05:00:00

DELTAS
       Dropped mixed style delta parsing
	   In Date::Manip 5.xx, a parsed delta could be written in the delta style

	      1:2:3

	   or in a language-specific expanded form:

	      1 hour 2 minutes 3 seconds

	   or in a mixed form:

	      1 hour 2:3

	   The mixed form has been dropped since I doubt that it sees much use in real life, and
	   by dropping the mixed form, the parsing is much simpler.

       Approximate date/date calculations
	   In Date::Manip 5.xx, the approximate delta between the two dates:

	      Jan 10 1996 noon
	      Jan  7 1998 noon

	   was +1:11:4:0:0:0:0 (or 1 year, 11 months, 4 weeks).  As of Date::Manip 6.0, the delta
	   is +2:0:-0:3:0:0:0 (or 2 years minus 3 days). Although this leads to mixed-sign
	   deltas, it is actually how more people would think about the delta. It has the
	   additional advantage of being MUCH easier and faster to calculate.

       Approximate relationships in deltas
	   When printing parts of deltas in Date::Manip::5.xx, the approximate relationship of 1
	   year = 365.25 days was used. This is the correct value for the Julian calendar, but
	   for the Gregorian calendar, a better value is 365.2425, and this is used in version
	   6.00.

       Old style formats
	   The formats used in the printf command are slightly different than in the old
	   Delta_Format command.

	   The old formats are described in the Date::Manip manual, and the new ones are in the
	   Date::Manip::Delta manual.

	   The new formats are much more flexible and I encourage you to switch over, however at
	   this point, the old style formats are officially supported for the Delta_Format
	   command.

	   At some point, the old style formats may be deprecated (and removed at some point
	   beyond that), but for now, they are not.

	   The old formats are NOT available using the printf method.

RECURRENCES
       The day field meaning changed in a few recurrences
	   The value of the day field can refer to several different things including the day of
	   week number (Monday=1 to Sunday=7), day of month (1-31), day of year (1-366), etc.

	   In Date::Manip 5.xx, it could also refer to the nth day of the week (i.e. 1 being the
	   1st day of the week, -1 being the last day of the week).  This meaning is no longer
	   used in 6.xx.

	   For example, the recurrence:

	      1*2:3:4:0:0:0

	   referred to the 3rd occurence of the 4th day of the week in February.

	   The meaning has been changed to refer to the 3rd occurence of day 4 (Thursday) in
	   February. This is a much more useful type of recurrence.

	   As a result of this change, the related recurrence:

	      1*2:3:-1:0:0:0

	   is invalid. Negative numbers may be used to refer to the nth day of the week, but NOT
	   when referring to the day of week numbers.

       Recurrence range now inclusive
	   Previously, the list of dates implied by the recurrence were on or after the start
	   date, but before the end date.

	   This has been changed so that the dates may be on or before the end date.

       Dropped support for a couple English recurrences
	   Date::Manip 5.xx claimed support for a recurrence:

	      every 2nd day in June [1997]

	   In actuality, this recurrence is not practical to calculate. It requires a base date
	   which might imply June 1,3,5,... in 1997 but June 2,4,6 in 1998.

	   In addition, the recurrence does not fit the mold for other recurrences that are an
	   approximate distance apart. This type of recurrence has a number of closely spaced
	   events with 11-month gaps between groups.

	   I no longer consider this a valid recurrence and support is now dropped for this
	   string.

	   I also dropped the following for a similar reason:

	      every 6th tuesday [in 1999]

       Other minor recurrence changes
	   Previously, ParseRecur would supply default dates if the start or end were missing.
	   This is no longer done.

DATE::MANIP FUNCTIONS
       The Date::Manip module contains the same functions that Date::Manip 5.xx had (though the
       OO modules do all the work now). In general, the routines behave the same as before with
       the following exceptions:

       Date_ConvTZ
	   Previously, Date_ConvTZ took 1 to 4 arguments and used the local time zone and the
	   ConvTZ config variable to fill in missing arguments.

	   Now, the Date_ConvTZ function only supports a 3 argument call:

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

	   If $from is not given, it defaults to the local time zone. If $to is not given, it
	   defaults to the local time zone.

	   The optional 4th argument ($errlevel) is no longer supported. If there is an error, an
	   empty string is returned.

       DateCalc
	   In Date::Manip 5.xx, it was recommended that you pass arguments to ParseDate or
	   ParseDateDelta. This is not recommended with 6.00 since it is much more intelligent
	   about handling the arguments, and you'll just end up parsing the date/delta twice.

BUGS AND QUESTIONS
       Please refer to the Date::Manip::Problems documentation for information on submitting bug
       reports or questions to the author.

SEE ALSO
       Date::Manip	  - main module documentation

LICENSE
       This script is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.

AUTHOR
       Sullivan Beck (sbeck@cpan.org)

perl v5.16.3				    2014-06-09		      Date::Manip::Changes5to6(3)
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