Here are some ways to express it, depending on the context:
For asking the time:
* He aha te wā? (What is the time?)
* Kua tae te wā? (Has the time arrived?)
* Kei te wā tenei? (Is this the time?)
For confirming a specific time:
* Koinei te wā? (Is this the time?)
* He tika tenei wā? (Is this time correct?)
For asking if it's time to do something:
* Kua tae te wā ki te... (Is it time to...?)
Remember, the best way to say it depends on the specific situation and the context of your conversation.