Two examples. (didactical purpose) 

#!/usr/bin/perl 
use strict;
use warnings;
use v5.10.0;
use Time::Piece;
use Time::Seconds;
use DateTime;


my $dt = DateTime->now( time_zone => 'floating' );

my $next = { 
    mon => ( $dt->mday >= 21 ? ( $dt->mon + 1 ) % 12 : $dt->mon ),
    year =>
      ( ( $dt->mon == 12 and $dt->mday >= 21 ) ? $dt->year + 1 : $dt->
+year ),
    day => 21, 
    hms => '12:00:00'
};

$next->{'dt'} = DateTime->new(
    year  => $next->{'year'},
    month => $next->{'mon'},
    day   => $next->{'day'},
    hour  => substr( $next->{'hms'}, 0, 2 ) 
);

my $t = localtime;

print Time::Seconds->new(
    Time::Piece->strptime(
        sprintf( "%s-%s-%sT%s",
            $next->{'year'}, $next->{'mon'}, $next->{'day'}, $next->{'
+hms'} ),
        "%Y-%m-%dT%T"
      ) - $t
)->seconds, "\n";

print $next->{'dt'}->subtract_datetime_absolute($dt)->seconds, "\n";

# Output :
#  1308641
#  1308641

[download]

In reply to Re: How to get time in seconds from localtime(time) to next 21st date of the month? by poolpi
in thread How to get time in seconds from localtime(time) to next 21st date of the month? by basman

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