ActiveSupport、Time#last_year
>> require "rubygems" => true >> require "active_support" => true >> Time.local(2008, 12, 31).last_year => Mon Dec 31 00:00:00 +0900 2007
>> require "rubygems" => true >> require "active_support" => true >> Time.local(2008, 12, 31).last_year => Mon Dec 31 00:00:00 +0900 2007