I agree with graff about using a Date:: module. How would you create the end given this start?

script.pl --start 'Dec 31 23:59'
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Consider the following:

use strict;
use warnings;
use Date::Parse;
use Date::Calc qw/Localtime/;

my $startDateTime = 'Dec 31 23:59:';
my $addMinutes    = 2;

my $year = ( Localtime(time) )[0];

$startDateTime .= '00 ' . $year;

my $startSeconds = str2time($startDateTime);
my $endSeconds   = $startSeconds + $addMinutes * 60;

print "\$startSeconds: $startSeconds; \$endSeconds: $endSeconds; Delta
+: "
  . ( $endSeconds - $startSeconds );
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Output:

$startSeconds: 1357027140; $endSeconds: 1357027260; Delta: 120
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You can use Date::Parse to convert a line's date/time string to seconds, and then print the line if the value's within the $startSeconds and $endSeconds range.