Check out Date::Manip

Some examples from the docs:

2. Compare two dates

  $date1=&ParseDate($string1);
  $date2=&ParseDate($string2);
  $flag=&Date_Cmp($date1,$date2);
  if ($flag<0) {
    # date1 is earlier
  } elsif ($flag==0) {
    # the two dates are identical
  } else {
    # date2 is earlier
  }
[download]

4. The amount of time between two dates.

  $date1=&ParseDate($string1);
  $date2=&ParseDate($string2);
  $delta=&DateCalc($date1,$date2,\$err);
    => 0:0:WK:DD:HH:MM:SS   the weeks, days, hours, minutes,
                            and seconds between the two
  $delta=&DateCalc($date1,$date2,\$err,1);
    => YY:MM:WK:DD:HH:MM:SS  the years, months, etc. between
                             the two
[download]

There are many more examples/"recipes" contained in the docs.

HTH