# 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