undated
adjective /ˌʌnˈdeɪtɪd/
  /ˌʌnˈdeɪtɪd/
- without a date written or printed on it未注日期的 - an undated letter一封没写日期的信 
 
- an undated letter
- of which the date is not known日期不明的;时间不详的 - undated archaeological remains时间未确定的考古遗迹 
 compare dated
- undated archaeological remains