This is PerlMonks "Mobile"

Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

If you're storing your dates as epoch seconds then simply subtract one from the other. If you've got a structured date (distinct year, day, month, hour, minute, seconds values) then use one of the Date::Manip and Date::Calc modules from CPAN.