included

# File activesupport/lib/active_support/core_ext/date/calculations.rb, line 6
        def self.included(base) #:nodoc:
          base.extend ClassMethods

          base.instance_eval do
            alias_method :plus_without_duration, :+
            alias_method :+, :plus_with_duration

            alias_method :minus_without_duration, :-
            alias_method :-, :minus_with_duration
          end
        end