APM: GMT question

[Mike Stok]

On Wed, 4 Dec 2002, Goldilox wrote:

> If I'm doing this:
> $timezoneoffset = -6;
> $offset = $timezoneoffset * 3600;
> ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst) = gmtime(time +
> $offset);
> 
> I am wondering if Windows vs Unix if any OS will account for DST (Daylight
> Savings Time)? My assumption is Windows will and Unix won't, but maybe there is
> a workaround for Unix (or maybe I'm wrong in my assumptions).

GMT (or UTC) doesn't have daylight savings, but localtime will tell you if 
the time in the local timezone uses DST or not.

Perl does deal with timezones and DST, try this and look at the output - 
gmtime never has daylight savings:

use POSIX qw/ tzset /;
use Time::Local;

use constant TORONTO => 'EST5EDT';  # -15C yesterday morning
use constant AUSTIN  => 'CST6CDT';  # considerably warmer...

my $now  = time;
my $then = timelocal(0, 0, 12, 1, 6, 2001);	# July

foreach my $time ($now, $then) {
    foreach my $timeZone (AUSTIN, TORONTO) {
        $ENV{'TZ'} = $timeZone;
        tzset;
        print "$time: $time, time zone $ENV{'TZ'}\n";
        print "     gmtime: @{[scalar(gmtime $time)]} @{[gmtime $time]}\n";
        print "  localtime: @{[scalar(localtime $time)]} @{[localtime $time]}\n";
        print "\n";
    }
}

Hope this helps,

Mike

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