Localtime() or gmtime()

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Re: Localtime() or gmtime() by swiftone (Curate) on Oct 14, 2002 at 21:18 UTC
Some quick experimentation on my system (Debian Linux) shows that changing $ENV{TZ} changes the results of localtime. I found some documentation at http://www.aota.net/Script_Installation_Tips/perltime.php4, and Googling for "perl $ENV{TZ}" will get you quite a bit of info. Hope that helps.	[reply]
Re: Localtime() or gmtime() by Flexx (Pilgrim) on Oct 15, 2002 at 00:52 UTC
Hi, Altering your `$ENV{TZ}`, for a very quick hack could do. A `local $ENV{TZ} = 'EET' # EET?` is a bit better. But beware (know what you do)! This is potentially dangerous, if you use `qx//` or `[system]()` calls, require other perl scripts/use modules, do IPC (interact with other running processes), have changing configuration (see below), etc. In a production script/environment you'll want to use a Date/Time manipulation module, like the excellent Date::Manip or Date::Calc. These will do what you need (and more), safely with regard to daylight saving times and/or configuration changes. Imagine what happens if your servers' sysop one day decides he'd switch his servers to use UTC as their RTC's timezone. These modules will return the correct date, simply adding the n hours offset will fail in such a case... Times are just data. Operate on it. If you want to know what time it is in Zimbabwe, you'd calculate the difference to your local time -- you wouldn't reset your wristwatch (i. e. change your configuration) to see what the time would be (I hope ;)... Hope this helps a bit, so long, Flexx	[reply] [d/l] [select]
Re: Localtime() or gmtime() by Abigail-II (Bishop) on Oct 15, 2002 at 08:20 UTC
Imagine what happens if your servers' sysop one day decides he'd switch his servers to use UTC as their RTC'S timezone. These modules will return the correct date, simply adding the n hours offset will fail in such a case... Times are just data. Operate on it. If you want to know what time it is in Zimbabwe, you'd calculate the difference to your local time So, what is it? Can you, or can't you calculate the difference? First you say you can't, then you say you can. Also, how would `Date::Manip` or `Date::Calc` continue to return "the correct date" when the server switches timezones (wrongly apparently, otherwise localtime() would return the correct time). Abigail	[reply] [d/l] [select]
Re: Localtime() or gmtime() by nothingmuch (Priest) on Oct 14, 2002 at 21:16 UTC
perhaps this is a bit makeshift, but have you considered altering the return from time() to add/deduct the correct number of hours and then apply localtime()? i am not sure, but i think pacific and east euro are 10 hours apart, so that should be `localtime(time() - 10 * 60 * 60);` [download] actually changing the time zone is very platform specific, and you probably want to ask your sysop instead of the people here. Perhaps the Time::Local module (standard distribution) will also be of some use to you. -nuffin zz zZ Z Z #!perl	[reply] [d/l]
Re: Localtime() or gmtime() by Abigail-II (Bishop) on Oct 15, 2002 at 08:15 UTC
Of course, it isn't as simple as that. The main problem is daylight savings time. The world doesn't switch at the same time - or does the Pacific coast switch to DST in the middle of the day? ;-) DST happens at different dates, different times, and with different differences in different timezones, and some zones don't switch at all. On Unix, you can often get the time in a different zone by setting the `TZ` environment variable properly. Abigail	[reply] [d/l]


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