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Past date display ( today - N) in shell
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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. Unable to determine Time Zone Please refer to the Date::Manip::TZ documentation for a discussion of this problem. Calculations appear to be off by an hour Within days of releasing 6.00, I got the following report: print DateCalc(ParseDate("2009/10/31"), "+1 day"), " "; print DateCalc(ParseDate("2009/11/01"), "+1 day"), " "; print DateCalc(ParseDate("2009/11/02"), "+1 day"), " "; produced: 2009110100:00:00 2009110123:00:00 2009110300:00:00 In other words, the second calculation appears to be off by one hour. In actuality, the result is correct. In the user's timezone, daylight saving time ended on Nov 1, and the results are correct. In America/New_York time (which has the same result), the calculation means that: 2009-11-01 00:00:00 EDT + 24 hours = 2009-11-01 23:00:00 EST which is correct. 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 will not add however. I have frequently been asked to add formats such as "the 15th of last month", or "Monday of next week". I will NOT add these date formats to Date::Manip. 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 made a firm decision that Date::Manip will NOT support this type of format now, or at any time in the future. 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. 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 :-) 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. 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 consists of 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. 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: o The version of Date::Manip you are using. You can get this by using the script: use Date::Manip; print DateManipVersion(1)," "; or use Date::Manip::Date; $obj = new Date::Manip::Date; print $obj->version(1)," "; o 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 v5.12.1 2010-01-12 Date::Manip::Problems(3)
