In or on time?

We use IN TIME when we want to say that someone is not late. I mean early enough to do something.
Example.
The meeting is at 6.30 p.m. And I arrive at 6:15.
I arrive IN time to drink a cup of coffee.

We use ON TIME when we are punctual.
Exampe:
The meeting is at 6:30 and I arrive at 6:30.