use Date::Calc qw(Delta_Days);
$days = Delta_Days( $year1, $month1, $day1, $year2, $month2, $day2);

##</code><code>##

use Date::Calc qw(Delta_DHMS);
($days, $hours, $minutes, $seconds) =
  Delta_DHMS( $year1, $month1, $day1, $hour1, $minute1, $seconds1,  # earlier
              $year2, $month2, $day2, $hour2, $minute2, $seconds2); # later