Trying doing a Super Search for "dates" you will find much wisdom including references to- Time::Local (sample code), localtime(), the POSIX module (which is part of core Perl), various CPAN date modules including Date::Calc and Date::Manip.

Or leaving the Monastery for a moment a Google search for dealing with dates in perl would lead you to The Perl You Need to Know Part 9: Time and Date Manipulation

--
Until you've lost your reputation, you never realize what a burden it was or what freedom really is. -Margaret Mitchell

set serveroutput on
declare
d1 date;
d2 date;
n1 number;
begin
d1 := sysdate;
d2 := sysdate - 1;
n1 := d1 - d2;
dbms_output.put_line(n1);
end;
/
[download]

rdfield