When you want to say, it’s time to or, the time has come to… Use chegou a hora. Literally, the hour arrived. It’s always followed by “de”. Like this:
Chegou a hora de dormir. (It's time to go to sleep.)
Chegou a hora de mudar. (It's time to change.)
Chegou a hora de pagar. (It's time to pay.)
Chegou a hora de partir. (It's time to leave.)
Note the verb following the “de” is always in the infinitive. When you say de dormir, for example – you are saying: to sleep.