advance

# File activesupport/lib/active_support/time_with_zone.rb, line 224
    def advance(options)
      # If we're advancing a value of variable length (i.e., years, weeks, months, days), advance from #time,
      # otherwise advance from #utc, for accuracy when moving across DST boundaries
      if options.detect {|k,v| [:years, :weeks, :months, :days].include? k}
        method_missing(:advance, options)
      else
        utc.advance(options).in_time_zone(time_zone)
      end
    end