Date Calculation in Rails

>> Date.new( 2008, 1, 1 ).to_time.advance( :months => 1 )
=> Fri Feb 01 00:00:00 +0000 2008

>> Date.new( 2008, 2, 1 ).to_time.advance( :months => 1 )
=> Sat Mar 01 00:00:00 +0000 2008

>> Date.new( 2008, 1, 1 ).to_time + 1.month
=> Thu Jan 31 00:00:00 +0000 2008

Extracted from here:

http://roninonrails.blogspot.com/2008/01/beware-of-rails-date-arithmetic.html