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Date::Manip::Changes5to6(3pm) User Contributed Perl Documentation Date::Manip::Changes5to6(3pm)
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
IntCharSet This has been replaced with better support for
international character sets. The Encoding config
variable may be used instead.
Other config variables deprecated
The following config variables are deprecated and will be removed in some future
version:
TZ Use SetDate or ForceDate 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.xx, 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 6.00, 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::DM5 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 occurrence of the 4th day of the week in February.
The meaning has been changed to refer to the 3rd occurrence 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 AT cpan.org)
perl v5.32.1 2021-11-20 Date::Manip::Changes5to6(3pm)
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