UTC offset

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

I'm trying to find my local UTF offset. For some reason, this is one hour too small (in absolute value):

$t = POSIX::mktime(localtime) - POSIX::mktime(gmtime);

I'm UTC -04:00, but that tells me that I'm only UTC -03:00. Can anyone explain why? (if it matters, I'm on Debian with "v5.8.4 built for i386-linux-thread-multi")

Update: I was being an idiot and was actually getting -05:00 instead of -04:00. Anyhow, the solution is to do

@g=gmtime;$g[8]=-1;$offset=POSIX::mktime(localtime)-POSIX::mktime(@g);

Since gmtime won't set DST, and when you're in it, that will mess you up (since mktime() takes local time, which in a DST timezone, expects to be in DST).

With humble thanks,
-Chris
--
"They laughed at Einstein. They laughed at the Wright Brothers. But they also laughed at Bozo the Clown." -- Carl Sagan

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Re: UTC offset by ikegami (Patriarch) on Jun 09, 2005 at 01:09 UTC
`>perl -le "use POSIX; print((POSIX::mktime(localtime) - POSIX::mktime( +gmtime)) / 60 / 60);" -5` [download] ...which is perfectly appropriate, since I'm in EST. If it was winter, I'd expect to see -4, because then I'd be in EDT. Maybe your OS's time zone isn't set right? Does the (unix) system tool `date` return the right time zone? The (linux and BSD) time zone is changed by altering to where the link /etc/localtime points. Where are you located, anyway?	[reply] [d/l] [select]
Re: UTC offset by mugwumpjism (Hermit) on Jun 09, 2005 at 01:23 UTC
To explore this problem, print; the values returned by list context `localtime` the values returned by list context `gmtime` Then, try passing `time() + 6 * 30 * 86400` as the explicit argument to both functions, and look at the same thing. You will see where the apparent anomaly is coming from. $h=$ENV{HOME};my@q=split/\n\n/,`cat $h/.quotes`;$s="$h/." ."signature";$t=`cat $s`;print$t,"\n",$q[rand($#q)],"\n"; [download]	[reply] [d/l]