無暝無日 [无－无－]

Jyutping mou4 暝 mou4 jat6
Pinyin wú míng wú rì

Definitions (Wiktionary)
  1. phrase, Hokkien, idiomatic
    day and night (doing a task unceasingly)
    (syn.) 沒日沒夜, 没日没夜, 無晝無暗, 无昼无暗