ActiveSupport、Date#ago
>> require "rubygems" => true >> require "active_support" => true >> Date.new(2008, 12, 31).ago(1) => Tue Dec 30 23:59:59 +0900 2008
>> require "rubygems" => true >> require "active_support" => true >> Date.new(2008, 12, 31).ago(1) => Tue Dec 30 23:59:59 +0900 2008