nonstop vs day-and-night

nonstop is a noun but day-and-night is not a noun.

Word	Noun	Adjective	Verb	Adverb
nonstop	Yes	Yes	No	Yes
day-and-night	No	Yes	No	No

As adjectives, nonstop and day-and-night are synonyms defined as:

Other synonyms of nonstop include around-the-clock, round-the-clock.

nonstop (noun)	day-and-night (noun)
a flight made without intermediate stops between source and destination

nonstop (adjective)	day-and-night (adjective)
at all times	at all times
(of a journey especially a flight) occurring without stops

nonstop (adverb)	day-and-night (adverb)
without stopping