in time/on time

Both "On time” and “in time” are two prepositional phrases that are somewhat confusing.  “On time” means at the planned or specified time; neither late nor early. It denotes being punctual:

Peter wants the meeting to start exactly on time.

Please, try to arrive on time for the programme.

“In time” means with enough time to spare; before the last moment:

The boy would have died if they hadn’t got him to the hospital in time.

It could also mean in the future or eventually:

In time, he will see that life is not a bed of roses.