code: function setSingleSchedule (date) {
    if (typeof date !== 'string') {
      throw new JError.InvalidArgumentError('date must be set to the string.')
    }
    var single = {
      'time': date
    }
    this.trigger = JUtil.extend(this.trigger, {
      'single': single
    })
    return this
  }
docs: 定时任务 start date: 必须为 YYYY-MM-DD HH:MM:SS 格式，如："2014-02-15 12:00:00"