#!/usr/bin/perl -w

use strict;
use Time::Local;

my %mon = (Jan => 0, Feb => 1, Mar => 2, Apr => 3, May => 4,
           Jun => 5, Jul => 6, Aug => 7, Sep => 8, Oct => 9,
           Nov => 10, Dec => 11);

sub parse_date {
  local $_ = shift;

  my ($mon, $day, $year, $hr, $min, $am_pm) = split /\W+/;

  $mon = $mon{$mon};
  $year -= 1900;

  $hr += 12 if ($am_pm eq 'PM' and $hr != 12);

  timelocal(0, $min, $hr, $day, $mon, $year);
}

while (<DATA>) {
  chomp;
  my ($start, $end) = split(/ & /);

  print parse_date($end) - parse_date ($start), "\n";
}

__END__
Mar 19, 2001 01:23 PM & Mar 19, 2001 03:52 PM
Mar 19, 2001 11:42 AM & Mar 19, 2001 12:21 PM
Feb 29, 2001 11:23 PM & Mar 01, 2001 12:12 AM