夜以繼日

Simplified: 夜以继日

On the HSK 7-9 vocabulary list, at CEFR level C1.

yèyǐjìrì ㄧㄝˋ ㄧˇ ㄐㄧˋ ㄖˋ

    • night and day (idiom) continuous strenuous effort

Character by character

Sources