continuously, without stop; round the clock

day and night; continuously without distinguishing between daytime and nighttime

to hide by day and come out at night

to travel at night and lie low by day

to turn day into night; to prolong one's pleasure regardless of the hour (idiom, from Book of Songs)

the equinox

the winter days are short and the nights long

diurnal; diurnality

to burn the midnight oil; to work through the night, making night as day

Zai Yu sleeps by day (idiom); refers to the story in the Analects where Confucius scolds his student for sleeping during lectures.

day and night (to toil, or to abandon oneself to pleasure without ceasing)