Date::Manip::Changes5tUserpContributed Perl DocumDate::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@cpan.org)
perl v5.36.0 2023-03-05 Date::Manip::Changes5to6(3pm)
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