Timeの差分

RailsでTimeオブジェクトを引き算した場合に日数を出したい場合

irb(main):072:0> today = Time.now
=> 2013-10-10 16:22:31 +0900
 

irb(main):073:0> beginning_of_month = Time.now.beginning_of_month
=> 2013-10-01 00:00:00 +0900

irb(main):074:0> (today - beginning_of_month).to_i/1.day
=> 9