Windows, Time::Local and dates before the epoch

barbie has asked for the wisdom of the Perl Monks concerning the following question:

I'm currently writing a module that uses Time::Local. In particular the timelocal() function. Now I also want to use dates before the epoch, the example I'm using is 13th September 1965 (a significant date in my calendar :)). On Linux this gives me the correct value with no problem. However, running on Windows via the test suite I get a whole host of error messages, although standalone it just reports the value correctly.

So I decided to have a look at what is going on inside timelocal(). Unfortunately the culprit seems to be localtime(). With negative values it prints nothing. Thankfully Time::Local can cope with this and still returns a valid negative number.

My problem now is how do I stop these warnings of "Use of uninitialized value in integer addition..." etc while running my tests? Bear in mind this a Perl function running from a Perl Core module.

Do I simply not allow tests of dates before the epoch if running on Windows (I'd rather not have to do that *), or is there some way I can tell localtime the world is not going to end or perhaps a switch for the test harness that can suppress them? Or is there another way?

* Though I note that Time::Local ignores dates before the epoch in tests ... hmmm, I wonder why.

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Barbie
Birmingham Perl Mongers
Web Site: http://birmingham.pm.org/
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Comment on Windows, Time::Local and dates before the epoch

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Re: Windows, Time::Local and dates before the epoch by fglock (Vicar) on Jun 11, 2003 at 14:52 UTC
You might try updating your Time::Local (there is a new version in CPAN). A better alternative would be to use DateTime instead. If you can't install DateTime, you can use Date::ICal. Both modules work with dates before 1970.	[reply]
Re: Re: Windows, Time::Local and dates before the epoch by barbie (Deacon) on Jun 11, 2003 at 15:10 UTC
Might be better to explain a little more about the module I'm writing. Calendar::List provides a list, hash or HTML code snippet of a set of dates. Underneath the hood is another module Calendar::Functions which uses one of DateTime, Date::ICal or Time::Local to do the date manipulation, depending which is installed. So, as I don't know what is going to be on the user's machine, and the latest version of Time::Local on CPAN has exactly the same problem, I'm looking for something a bit easier to implement. Note the problem is ONLY in the test suite. Outside of the test suite it's fine. The warning messages don't appear. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Barbie Birmingham Perl Mongers Web Site: http://birmingham.pm.org/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~	[reply]
Re: Windows, Time::Local and dates before the epoch by Skeeve (Parson) on Jun 12, 2003 at 05:24 UTC
When I read your reply to fglock I thought: How about implementing your own functions? You won't have to depend on anything preinstalled on the client then. At least calculating a number from any date is not so difficult. The way back is a bit more complicated but not unsolvable. I did that more than once for my faithful FX-602P (a programmable pocket calculator) and for (Turbo-)Pascal ages ago. Maybe I have the source somewhere or can recreate it from mind if you're interested.	[reply]
Re: Re: Windows, Time::Local and dates before the epoch by barbie (Deacon) on Jun 12, 2003 at 11:45 UTC
You mean write yet another Date/Time module that does more or less the same as the others. I'd be hung, drawn and quartered :) I didn't want to write another module, simply because DateTime and Date::ICal are both well supported modules. If someone using my module wants reliable handling of dates then they are advised to install a reliable date handling module. Time::Local is the fallback simply because its in the Core. Since yesterday I'm thinking along the same lines as Time::Local tests. If the user is happy with the boundaries set by Time::Local and localtime, then I don't really need tests that look beyond that. If they want to go beyond those boundaries then they should really install a more reliable date handling module. I just found it infuriating having done all these tests and got it working on Linux, when I test it on Windows all these messages suddenly appeared. Such is life. -- Barbie \| Birmingham Perl Mongers \| http://birmingham.pm.org/	[reply]
Re: Re: Re: Windows, Time::Local and dates before the epoch by Skeeve (Parson) on Jun 12, 2003 at 13:17 UTC
You mean write yet another Date/Time module that does more or less the same as the others. I'd be hung, drawn and quartered :) I know. They did it to me after posting my reply. Downvoted almost instantly ;-) Nevertheless. If it's just a small routine, I prefer to use my own algorithm in favour of using just another library that need to be installed and that I need to learn to handle ;-) If someone using my module wants reliable handling of dates then they are advised to install a reliable date handling module That's fair and if you can live with it... okay for me :-) Maybe I will get hanged. I will try and write YADCM (Yet Another Date Calculation Module).	[reply]