Is there a way I can fool localtime() into giving me the EST time or any other idea for how to get the current EST time from a CET-based machine?

DateTime.pm makes this trivial.

$ perl -MDateTime -le 'print DateTime->now(time_zone => "EST")'
2006-07-17T04:37:59
[download]

You can set $ENV{TZ} and then use the tzset from POSIX:

use POSIX qw(tzset);
use strict;
                                                                      
+          
print scalar localtime();
                                                                      
+          
$ENV{TZ} = 'EST';
                                                                      
+          
tzset();
                                                                      
+          
print scalar localtime();
[download]

/J\

Actually you might want to use:

use POSIX qw( tzset )

sub localtime_in { local $ENV{TZ} = shift; tzset; localtime }

$localtime_in_EST = localtime_in( "EST" );
[download]

Otherwise you've globally change the timezone for any other calls to (gm|local)time elsewhere in your code.

And personally I've used both some variant of twiddling $ENV{TZ} like this and DateTime.

Localising the $ENV{TZ} isn't sufficient to prevent the effect being global, tzset() will need to be called after the value has been reverted to restore the timezone used by localtime(). For example:

use POSIX qw(tzset);
use strict;
                                                                      
+          
print scalar localtime();
                                                                      
+          
sub localtime_in
{
   local $ENV{TZ} = 'EST';
                                                                      
+          
   tzset();
                                                                      
+          
   localtime();
}
                                                                      
+          
print scalar localtime_in();
print scalar localtime();
[download]

Off the top of my head a way of fixing that would be something like:

use POSIX qw(tzset);
use strict;
                                                                      
+          
print scalar localtime();
                                                                      
+          
sub localtime_in
{
   my $rc;
   my @rc;
   {
     local $ENV{TZ} = shift;
     tzset();
     wantarray ? @rc = localtime() : $rc = localtime();
   }
   tzset();
   return wantarray ? @rc : $rc;
}
                                                                      
+          
print scalar localtime_in('EST');
print scalar localtime();
[download]

/J\

Doesn't seem to work for me using ActivePerl v5.8.7 build 813 under Windows Server 2003. I do get the local time no matter whether I set $ENV{TZ} to EST or CET (my timezone). Tried even localtime_in( "0500" );

Update: The DateTime solution works though. So if you need to make portable code, use DateTime;

Jenda


Support Denmark! Defend the free world!

Storing UTC makes it trivial to display correct localised date-times in Perl / various web and other front ends / languages etc using standard libraries, and without adding the overhead of your own complex date-math for all accesses to the data.

As an aside, MySQL <= 4.1 is a PITA for saving UTC - all the time functions are localtime, and affected by the TZ of your mysql daemon.

Use this expression for a UTC now() in MySQL:

  update mytable
  set right_now=DATE_ADD('1970-01-01', INTERVAL UNIX_TIMESTAMP() SECON
+D)
[download]

Update: OK to be honest I did not explicitly use 'local' because the tzset had to be repeated anyway. What I actually did was more like:

sub RemoteTime {
    my $realtz = $ENV{ TZ };
    my ( @return, $return );
    my $wantarray = wantarray;
    $ENV{ TZ } = shift;
    tzset;
    if ( $wantarray ) {
        @return = localtime();
    }
    else
        $return = localtime();
    }
    $ENV{ TZ } = $realtz;
    tzset;
    return $wantarray ? @return : $return;
}
[download]

If you need to compute stuff you really ought to use DateTime - it takes care of all the nasty details of time math for you.
-nuffin
zz zZ Z Z #!perl