in reply to How to get TZ difference?

One way might be to use Perl's localtime and gmtime functions. Something like this should work. 
$local=(localtime)[2];
$gmt=(gmtime)[2];
$diff=$gmtime-$local;  #depending on which side of the line you are on

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Time flies like an arrow, fruit flies like banannas

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Re: Re: How to get TZ difference?
by sgifford (Prior) on Jun 28, 2003 at 16:56 UTC
    This doesn't work when localtime and gmtime are on different days (ie, in zone GMT+4 between 8:00pm and 11:59pm). Here's a fixed version: 
    #!/usr/bin/perl

@local=(localtime);
@gmt=(gmtime);
$diff=$gmt[2]-$local[2];
if ($gmt[5] > $local[5] || $gmt[7] > $local[7])
{
  $diff += 24;
}
elsif ($gmt[5] < $local[5] || $gmt[7] < $local[7])
{
  $diff -= 24;
}

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[reply]
[d/l]
      This is a little shorter and more confusing. 
        @local=(localtime(time+$off_h*60*60));
  @gmt=(gmtime(time+$off_h*60*60));
  $diff=$gmt[2]-$local[2] + ($gmt[5] <=> $local[5] 
                                     || 
                             $gmt[7] <=> $local[7])*24;

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[reply]
[d/l]
        Hi,

        Thanks for your idea. But let me ask you what is $off_h here? And I found that correct result occurs when I subtract $gmt[2] from $local[2]: 

        $diff=$local[2]-$gmt[2] + ($gmt[5] <=> $local[5] 
                                   || 
                           $gmt[7] <=> $local[7])*24;

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        --dda

[reply]
[d/l]
[select]
      thanks for the correction

      Time flies like an arrow, fruit flies like banannas

[reply]
      you forgot to compare the months in case when we have last day of the month, around midnight it will return inccorect results
[reply]
        perl -e 'print ( ( (localtime)[2] - (gmtime)[2] + 12 ) % 24 - 12 )'

        ...works across midnight, end of month, etc without all those pesky conditionals. Works because perl has a useful definition of modulo operator (%) for negative operands, but beware this can be compromised in certain situations. See perlop#Multiplicative-Operators.

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[d/l]

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