code: func (d Duration) ConvertToTime(tp uint8) (Time, error) {
  	year, month, day := gotime.Now().Date()
  	// just use current year, month and day.
  	n := gotime.Date(year, month, day, 0, 0, 0, 0, gotime.Local)
  	n = n.Add(d.Duration)
  
  	t := Time{
  		Time: FromGoTime(n),
  		Type: mysql.TypeDatetime,
  		Fsp:  d.Fsp,
  	}
  
  	return t.Convert(tp)
  }
docs: // ConvertToTime converts duration to Time.
  // Tp is TypeDatetime, TypeTimestamp and TypeDate.