夜以继日 (yè yǐ jì rì): Day and night / round the clock (adverb/idiom) — Meaning & Stroke Order

In order to finish the project on time, they worked day and night.

To overcome the technical difficulties, the R&D team worked day and night conducting experiments and debugging.

You've been working overtime day and night recently, can your body handle it?

To prepare for the exam, the students study day and night.