    # File lib/core/facets/time/shift.rb, line 77
      def less(*time_units)
        time_hash  = Hash===time_units.last ? time_units.pop : {}
        time_units = time_units.flatten

        time_units << :seconds if time_units.size % 2 == 1

        time_hash.each{ |units, number| time_units << number; time_units << units }

        neg_times = []
        time_units.each_slice(2){ |number, units| neg_times << -number; neg_times << units }

        shift(*neg_times)
      end