ActiveSupport、Time#end_of_quarter, Time#at_end_of_quarter
>> require "rubygems" => true >> require "active_support" => true >> Time.local(2008, 12, 31).end_of_quarter => Wed Dec 31 23:59:59 +0900 2008 >> Time.local(2008, 1, 31).end_of_quarter => Mon Mar 31 23:59:59 +0900 2008 >> Time.local(2008, 12, 31).at_end_of_quarter => Wed Dec 31 23:59:59 +0900 2008