Which one is correct: sleep time or sleeping time?

It is 'sleep time'.

Sleep time is between 9:00pm and 6:00am

North American English generally prefers the root verb: Sleep time, swin suit, spark plug;

British English usually prefers the participle: Sleeping time, swimming costume, sparking plug.

Some people might claim to see some semantic difference between the two, but this is only because some Brits will always go for the American form, so that both forms do occur in modern British English. Traditionally, and to a large extent, even today, the choice is one of dialect: North American versus British.

Sleep time would be correct by my opinion. Because if you say "sleeping time" you might say that the time is sleeping ^_^. But they are both accepted in eglish litelature so write which ever you wnat. Not a terrible difference.

SLEEP TIME is the correct one. Because sleeping time is the continues tense

It would depend on context and probably in which English-speaking country you were. 'Sleep time' sounds more American, 'sleeping time' sound more British.

sleeping time is the right word...

Bed time.