# File lib/rufus/scheduler/util.rb, line 188
    def self.to_duration(seconds, options={})

      h = to_duration_hash(seconds, options)

      return (options[:drop_seconds] ? '0m' : '0s') if h.empty?

      s =
        DU_KEYS.inject('') { |r, key|
          count = h[key]
          count = nil if count == 0
          r << "#{count}#{key}" if count
          r
        }

      ms = h[:ms]
      s << ms.to_s if ms

      s
    end