def enqueue_at(timestamp, method, *args)
      offset = Time.at(timestamp).to_i - Time.now.to_i
      enqueue_in(offset, method, *args)
    end
def enqueue_at(timestamp, method, *args)
      offset = Time.at(timestamp).to_i - Time.now.to_i
      enqueue_in(offset, method, *args)
    end
enqueue_at(t,m,a) inserts a row into the jobs table representing a job
 to be executed not before the specified time.
 The time argument must be a Time object or a float timestamp. The method
 and args argument must be in the form described in the documentation for
 the #enqueue method.
 This method returns a hash with the id of the enqueued job.