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

NAME
       Date::Manip::Problems - problems and bugs

KNOWN PROBLEMS
       The following are not bugs in Date::Manip, but they may give some people problems.

       Memory leak
	   There is a known memory leak in perl related to named regexp captures that directly
	   affects Date::Manip . The leak is in all versions of perl up to the following
	   versions:

	      5.10.1
	      5.12.5
	      5.14.3
	      5.15.5

	   The bug has been fixed in:

	      5.15.6
	      5.16.0

	   If a maintenance release is done for any of the other releases (5.10, 5.12, 5.14),
	   that includes the patch, I'll update this section to include that information.

	   Date::Manip 5.xx is not susceptible, so using it may be a feasible workaround, but if
	   you need accurate timezone handling, this isn't possible.

	   Simple tests estimate the leak to be about 3 MB per 10,000 dates parsed, so unless
	   you're parsing hundreds of thousands, or millions of dates, the leak probably won't be
	   a problem on systems with moderate amounts of memory. And if you're parsing that many
	   dates, the relatively slow Date::Manip may not be the correct module for you to use
	   anyway.

       Unable to determine Time Zone
	   Please refer to the Date::Manip::TZ documentation for a discussion of this problem.

       Dmake error on strawberry perl
	   Users of Strawberry perl on windows may encounter an error similar to the following:

	      dmake: makefile: line 3016: Error: -- Input line too long, increase MAXLINELENGTH

	   This is a known problem with some versions of strawberry perl, and I can't fix it in
	   Date::Manip.  If you encounter this problem, you can install the package manually
	   using the commands:

	      c:> cpan
	      cpan> look Date::Manip::Date
	      > perl Makefile.PL
	      > dmake MAXLINELENGTH=300000 make
	      > dmake MAXLINELENGTH=300000 make test
	      > dmake MAXLINELENGTH=300000 make install

	   You can find more details here:

	      http://www.nntp.perl.org/group/perl.win32.vanilla/2011/02/msg287.html

       Calculations appear to be off by an hour
	   Due to daylight saving time (specifically, the spring change where the time typically
	   moves forward from 02:00 to 03:00, any date calculation which would intuitively report
	   a time in that range will also move forward (or backward as the case may be).

	   *NOTE* This should be less of a problem since 6.30 with the addition of semi-exact
	   deltas.

       Missing date formats
	   Due to the large number of date formats that Date::Manip CAN process, people often
	   assume that other formats that they want to use should work as well, and when they
	   don't, it comes as a surprise.

	   With the much improved parsing of 6.00, many formats can be added easily, though
	   unless they are of general use, I'll probably suggest that you use parse_format
	   instead.

	   There is a class of formats that I do not plan to add however.

	   I have frequently been asked to add formats such as "the 15th of last month", or
	   "Monday of next week". I do not intend to add these date formats to Date::Manip, but
	   since I have received the request several times, I decided to include my reasoning
	   here.

	   Date::Manip can parse pretty much any static date format that I could think of or find
	   reference to. Dates such as "today", "Jan 12", or "2001-01-01" are all understood.

	   These are fairly limited however. Many very common date formats are best thought of as
	   a date plus a modification. For example, "yesterday" is actually determined internally
	   as "today" plus a modification of "- 1 day".  "2nd Sunday in June" is determined as
	   "June 1" modified to the 2nd Sunday.

	   As these types of formats were added over time, I quickly realized that the number of
	   possible date plus modification formats was huge. The number of combinations has
	   caused the parsing in Date::Manip to be quite complex, and adding new formats
	   occasionally causes unexpected conflicts with other formats.

	   The first time I received a request similar to "the 15th of last month", I intended to
	   add it, but as I analyzed it to see what changes needed to be made to support it, I
	   realized that this needed to be expressed as a date plus TWO modifications. In other
	   words, today modified to last month modified to the 15th day of the month.

	   As bad as date plus modification formats are, a date plus TWO modifications would be
	   exponentially worse. On realizing that, I decided that Date::Manip will not support
	   this type of format.

	   Although I apologize for the inconvenience, I do not intend to change my position on
	   this.

       Date::Manip is slow
	   NOTE: The following section applies primarily to 5.xx. I'm doing a lot of work to
	   optimize Date::Manip and I will rewrite this section to take this into account, and to
	   provide performance suggestions. It should be noted that initial tests show version
	   6.xx to be around twice as fast as 5.xx (though still considerably slower than some of
	   the other modules).

	   Date::Manip is probably one of the slower Date/Time modules due to the fact that it is
	   huge and written entirely in perl.

	   Some things that will definitely help:

	   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.

	   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).  Who
	   needs a business date more accurate than "6 to 8 weeks" anyway, right :-)

       Using functions/methods which are not supported
	   There have been a handful of incidents of people using a function from Date::Manip
	   which were not documented in the manual.

	   Date::Manip consists of a large number of user functions which are documented in the
	   manual. These are designed to be used by other programmers, and I will not make any
	   backwards incompatible changes in them unless there is a very compelling reason to do
	   so, and in that case, the change will be clearly documented in the
	   Date::Manip::Changes6 documentation for this module.

	   Date::Manip also includes a large number of functions which are NOT documented. These
	   are for internal use only.  Please do not use them!	I can (and do) change their use,
	   and even their name, without notice, and without apology!  Some of these internal
	   functions even have test scripts, but that is not a guarantee that they will not
	   change, nor is any support implied. I simply like to run regression tests on as much
	   of Date::Manip as possible.

	   As of the most recent versions of Date::Manip, all internal functions have names that
	   begin with an underscore (_). If you choose to use them directly, it is quite possible
	   that new versions of Date::Manip will cause your programs to break due to a change in
	   how those functions work.

	   Any changes to internal functions will not be documented, and will not be regarded by
	   me as a backwards incompatibility. Nor will I (as was requested in one instance)
	   revert to a previous version of the internal function.

	   If you feel that an internal function is of more general use, feel free to contact me
	   with an argument of why it should be "promoted".  I welcome suggestions and will
	   definitely consider any such request.

       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, and I do not intend to try to workaround this problem.

KNOWN COMPLAINTS
       Date::Manip 6.xx has gotten some complaints (far more than 5.xx if the truth be told), so
       I'd like to address a couple of them here.  Perhaps an understanding of why some of the
       changes were made will allay some of the complaints.  If not, people are always welcome to
       stick with the 5.xx release. I will continue to support the 5.xx releases for a couple
       years (though I do NOT plan to add functionality to it).

       These complaints come both from both the CPAN ratings site:

	  http://cpanratings.perl.org/dist/Date-Manip

       and from personal email.

       Requires perl 5.10
	   The single most controversial change made in 6.00 is that it now required perl 5.10.0
	   or higher. Most of the negative feedback I've received is due to this.

	   In the past, I've avoided using new features of perl in order to allow Date::Manip to
	   run on older versions of perl.  Prior to perl 5.10, none of the new features would
	   have had a major impact on how Date::Manip was written so this practice was justified.
	   That all changed with the release of perl 5.10.

	   One of the aspects of Date::Manip that has received the most positive response is the
	   ability to parse almost every conceivable date format.  Unfortunately, as I've added
	   formats, the parsing routine became more and more complicated, and maintaining it was
	   one of the least enjoyable aspect in maintaining Date::Manip . In fact, for several
	   years I've been extremely reluctant to add new formats due to the fact that too often,
	   adding a new format broke other formats.

	   As I was rewriting Date::Manip, I was looking for ways to improve the parsing and to
	   make maintaining it easier. Perl 5.10 provides the feature "named capture buffers".
	   Named capture buffers not only improves the ease of maintaining the complex regular
	   expressions used by Date::Manip, it makes it dramatically easier to add additional
	   formats in a way that is much less likely to interfere with other formats. The parsing
	   in 6.00 is so much more robust, extensible, and flexible, that it will make parser
	   maintenance possible for many years to come at a fraction of the effort and risk.

	   It was too much to turn down. Hopefully, since 5.10 has been out for some time now,
	   this will not prohibit too many people from using the new version of Date::Manip. I
	   realize that there are many people out there using older versions of perl who do not
	   have the option of upgrading perl.  The decision to use 5.10 wasn't made lightly...
	   but I don't regret making it. I apologize to users who, as a result, cannot use 6.00 .
	   Hopefully in the future you'll be able to benefit from the improvements in 6.00.

	   One complaint I've received is that this in some way makes Date::Manip backwards
	   incompatible, but this is not an accurate complaint. Version 6.xx DOES include some
	   backwards incompatibilities (and these are covered in the Date::Manip::Migration5to6
	   document), however in almost all cases, these incompatibilities are with infrequently
	   used features, or workarounds are in place to allow deprecated features to continue
	   functioning for some period of time.

	   Though I have no data to confirm this, I suspect that 90% or more of all scripts which
	   were written with Date::Manip 5.xx will continue to work unmodified with 6.xx (of
	   course, you should still refer to the migration document to see what features are
	   deprecated or changed to make sure that you don't need to modify your script so that
	   it will continue to work in the future). Even with scripts that need to be changed,
	   the changes should be trivial.

	   So, Date::Manip 6.xx is almost entirely backward compatible with 5.xx (to the extent
	   that you would expect any major version release to be compatible with a previous major
	   version).

	   The change is only in the requirements necessary to get Date::Manip 6.xx to run.

	   Obviously, it's not reasonable to say that Date::Manip should never be allowed to
	   switch minimum perl versions. At some point, you have to let go of an old version if
	   you want to make use of the features of the newer version. The question is, did I jump
	   to 5.10 too fast?

	   The negative ratings I see in the CPAN ratings complain that I no longer support perl
	   5.6 and perl 5.8.

	   With respect to 5.6, perl 5.6 was released in March of 2000 (that's before Windows XP
	   which was released in 2001). To be honest, I don't really feel much sympathy for this
	   complaint. Software that is 9 years old is ANCIENT. People may choose to use it... but
	   please don't complain when new software comes out that doesn't support it.

	   The argument for perl 5.8 is much more compelling. Although 5.8 was released quite
	   some time ago (July of 2002), there were no major perl releases until 5.10 came out in
	   December of 2007, so 5.8 was state-of-the art as little as 2 years prior to the
	   release of Date::Manip 6.xx.

	   I agree completely with the argument that abandoning 5.8 only 2 years after it was the
	   current version is too soon. For that reason, I will continue to support the
	   Date::Manip 5.xx releases for some years to come. I don't know exactly how long I'll
	   continue to support them, but it'll be at least 2-3 years. Once perl 5.10 is 5 years
	   old, I'll be much more likely to drop support for the 5.xx releases, but I DO want to
	   make use of the features of 5.10 for future development.  They make development so
	   much easier, and the parsing so much more robust (something I've wanted for years),
	   that I'm not willing to give up the advantages of 5.10.

	   But the next complaint is relevant.

       Automatic installs break
	   A much more important problem is that versions 6.00 through 6.07 broke automatic
	   installs for older perl installations. If you try to install Date::Manip using the
	   automatic tools (cpan/cpanp), they will look for the most recent version. If you are
	   using a version of perl older than 5.10, this fails, and rather than looking for an
	   older version, the tool simply reports a failure in installing Date::Manip.
	   Technically, the problem is not due to Date::Manip itself, but is a result of how perl
	   modules are currently managed.  However, since Date::Manip is managed by then, it's
	   important to avoid causing this type of problem (which I clearly failed to do).

	   As of Date::Manip 6.10, this problem should no longer occur. Starting with version
	   6.10, both the 5.xx and 6.xx versions of Date::Manip have been combined into a single
	   distribution (so Date-Manip-6.10 contained both Date::Manip 6.10 and Date::Manip
	   5.57). From Date::Manip 6.10 to 6.13, the perl version was determined at install time
	   and either the 5.xx or 6.xx version was installed.  From Date::Manip 6.14 on, both
	   versions are installed, and at run time, the correct version will be chosen (and if
	   you're running a recent version of perl, you can select to run the old or new
	   version).

	   All future version (for as long as 5.xx is supported) will include both the most
	   current 5.xx and 6.xx releases of Date::Manip. In this way, automatic install tools
	   will be able to install Date::Manip regardless of which version of perl you are
	   running.

       Too many modules
	   One minor complaint is that there are too many files. One person specifically objects
	   to the fact that there are over 470 modules covering non-minute offsets. This
	   complaint is (IMO) silly.

	   Date::Manip supports ALL historical time zones, including those with non-minute
	   offsets, and so there will be information for those time zones, even though they are
	   not currently in use.

	   I could of course store all of the information in one big module, but that means that
	   you have to load all of that data every time you use Date::Manip, and I find that to
	   be a very poor solution. Instead, storing the information in a per-time zone and per-
	   offset manner dramatically decreases the amount of data that has to be loaded.

	   While it is true that Date::Manip includes over 900 modules for all of the time zone
	   information, most implementations of time zone handling also choose to break up the
	   data into a large number of files.

	   My linux distribution (openSuSE 11.2 at the time of writing this) uses the standard
	   zoneinfo database, and at this point, there are over 1700 files included in
	   /usr/share/zoneinfo (though it does appear that there is some duplication of
	   information). Current versions of RedHat also use over 1700 files, so Date::Manip
	   isn't treating the time zone data in a new or unreasonable way.

       Objects are large
	   One complaint that was put on the CPAN ratings site was that the OO interface is "a
	   dud" due to the size of it's objects. The complaint is that a Date::Manip::Date object
	   is 115K while it should (according to the complaint) only require that you need to
	   save the seconds from the epoch, zone, and a couple other pieces of information, all
	   of which could probably be stored in 100 bytes or less.

	   This complaint is not accurate, and comes from a misunderstanding of how Date::Manip
	   objects are created.

	   Date::Manip is very configurable, and contains a great deal of information which could
	   theoretically be calculated on the fly, but which would greatly reduce it's
	   performance. Instead, in the interest of improving performance, the data is cached,
	   and since the data is virtually all potentially object specific, it has to be somehow
	   linked to the object.

	   For example, Date::Manip allows you to parse dates in several languages.  Each
	   language has a large number of regular expressions which are used to do the actual
	   parsing. Instead of recreating these regular expressions each time they are needed,
	   they are created once and stored in an object (specifically, a Date::Manip::Base
	   object).  The size of the Date::Manip::Base object is almost 15K (due primarily to the
	   regular expressions used in parsing dates in the selected language).

	   Similarly, a description of the time zones are stored in a second object (a
	   Date::Manip::TZ object).  The size of the Date::Manip::TZ object starts at 100K. That
	   may seem excessive, but you have to remember that there are almost 500 time zones, and
	   they have to be indexed by name, alias, abbreviation, and offset, and by the time you
	   do this, it does take a fair bit of space.  It should also be noted that the full
	   description of each timezone is only stored in the object when the timezone is
	   actually used, so if you use a lot of timezones, this object will grow slowly as new
	   timezones are used.

	   The size of the actual Date::Manip::Date object is a little over 300 bytes.	However,
	   each includes a pointer to a Date::Manip::Base and a Date::Manip::TZ object (and due
	   to how the object was being looked at in the complaint, they were reporting the size
	   of all three objects, NOT just the Date::Manip::Date object).

	   Both the Date::Manip::Base and Date::Manip::TZ objects are reused by any number of
	   Date::Manip::Date objects. They can almost be thought of as global data, except that
	   they are accessible in the standard OO manner, and you are allowed to modify them on a
	   per-object basis which WILL mean that you have to store more data. If you work with
	   multiple configurations (see Date::Manip::Config), you'll need multiple Base and TZ
	   objects. However, most of the time you will not need to do this.

	   The actual Date::Manip::Date object is a bit larger than suggested in the complaint,
	   but it should be noted that Date::Manip actually stores the dates in a number of
	   different formats (a string of the form YYYYMMDDHH:MN:SS and a list
	   [YYYY,MM,DD,HH,MN,SS] in the time zone it was parsed in, the local time zone (if
	   different) and GMT. By caching this information as it is used, it has a huge impact on
	   the performance.

	   So, Date::Manip in typical usage consists of one 100K Date::Manip::TZ object, one 15K
	   Date::Manip::Base objects, and any number of small 300 byte Date::Manip::Date objects.
	   Date::Manip::Delta objects are even smaller. Date::Manip::Recur objects are also
	   small, but they contain any number of Date objects in them.

	   I am certainly open to suggestions as to how I can improve the OO interface... but I
	   don't believe it is a dud. While I'm not an expert at OO programming, I believe that I
	   followed pretty standard and accepted procedures for accessing the data.

	   Please refer to the Date::Manip::Objects document for more information.

       Date::Manip has an inconsistent interface
	   I've gotten a few complaints that the interface to Date::Manip is inconsistent... and
	   I agree (at least when using the functional interfaces).

	   Date::Manip was originally written in an unplanned way... as a need/want came up, it
	   was extended. That's not the way to write a major package of course, but it wasn't
	   expected to be a major package at the start.

	   As it became more and more widely used, I too wished for a more consistent interface,
	   but I did not want to break backward compatibility for everyone using it.

	   When 6.xx was written, I spent a good deal of time trying to make a very standard OO
	   interface, so I do not believe that this complaint can be applied to the OO interface
	   (though I'm interested in suggestions for improving it of course).

	   As far as the functional interface goes, I'll continue to support it in a backward
	   compatible (and therefore inconsistent) form. I'd encourage the use of the OO
	   interface whenever possible.

BUGS AND QUESTIONS
       If you find a bug in Date::Manip, please send it directly to me (see the AUTHOR section
       below).	Alternately, you can submit it on CPAN. This can be done at the following URL:

	  http://rt.cpan.org/Public/Dist/Display.html?Name=Date-Manip

       Please do not use other means to report bugs (such as Usenet newsgroups, or forums for a
       specific OS or Linux distribution) as it is impossible for me to keep up with all of them.

       When filing a bug report, please include the following information:

       Date::Manip version
	   Please include the version of Date::Manip you are using.  You can get this by using
	   the script:

	      use Date::Manip;
	      print DateManipVersion(1),"\n";

	   or

	      use Date::Manip::Date;
	      $obj = new Date::Manip::Date;
	      print $obj->version(1),"\n";

       Perl information
	   Please include the output from "perl -V"

       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.  Start by reading the main Date::Manip
       documentation, and the other documents that apply to whatever you are trying to do.  If
       this still doesn't answer your question, mail me directly.

       I would ask that you be reasonably familiar with the documentation BEFORE you choose to do
       this. Date::Manip is a hobby, and I simply do not have time to respond to hundreds of
       questions which are already answered in this manual.

       If you find any problems with the documentation (errors, typos, or items that are not
       clear), please send them to me. I welcome any suggestions that will allow me to improve
       the documentation.

KNOWN BUGS
       None known.

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::Problems(3)


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