in reply to Is there an official DST border day detection module?

sub today_is_24hours {
    my $now = 60*60*int( time()/60/60 );   # Start of this hour
    my $hour = ( localtime($now) )[2];
    $now -= $hour*60*60;                   # Start of this day
    return ( localtime($now) )[8] == ( localtime($now+24*60*60) )[8];
}

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(DST never changes twice in a single day.)

- tye        

  • Comment on Re: Is there an official DST border day detection module? (localtime)
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Re^2: Is there an official DST border day detection module? (localtime)
by flowdy (Scribe) on Oct 28, 2014 at 10:17 UTC
    Hi tye,

    thanks to you a lot. As I want to get amount of hours in the day, I tried to modify your suggestion to:

    sub hours_in_day {
    my $now = 60*60*int( shift()/60/60 );   # Start of this hour
    my $hour = ( localtime($now) )[2];
    $now -= $hour*60*60;                   # Start of this day
    $hour = ( localtime($now+24*60*60) )[2];
    $hour -= 24 if int($hour/12);
    return 24-$hour;
}

    [download]

    But it is not working, hm ...

    Thinking & probing,
    flowdy

[reply]
[d/l]

      I think your logic is slightly amiss when you calculate the "start of this day". This variant works for me:

      #!/usr/bin/perl -Tw

use strict;

print "Today: " . hours_in_day (time) . "hours.\n";
print "Sun: " . hours_in_day (time-170000) . "hours.\n";

sub hours_in_day {
    my $now = 60*60*int( shift()/60/60 );   # Start of this hour
    my $hour = ( localtime($now) )[2];
    $now -= $hour*60*60;                    # Offset from start of thi
+s day
    $hour = ( localtime($now) )[2];
    $hour += 24 unless int($hour/12);
    return $hour;
}

      [download]

      and gives this output for me (Sunday was the switch from BST to GMT here):

      Today: 24hours.
Sun: 25hours.

      [download]
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