Try Date::Manip.

use warnings; use strict;
use Date::Manip::Date 6.30; 
my $today = Date::Manip::Date->new("today");
print $today->printf("Today is: %Y-%m-%d\n");
my $month_ago = $today->calc($today->new_delta("-1 months"));
print $month_ago->printf("A month ago from today is: %Y-%m-%d\n");
my $thirty_ago = $today->calc($today->new_delta("-30 days"));
print $thirty_ago->printf("Thirty days ago from today is: %Y-%m-%d\n")
+;
__END__
[download]

The output today is this:

Today is: 2014-04-18
A month ago from today is: 2014-03-18
Thirty days ago from today is: 2014-03-19
[download]

There's a difference between the two because March had 31 days.