On time means at a particular designated time, i.e. neither especially early nor late. The train is scheduled to arrive on time at 13:36.

In time means early enough, i.e. before a deadline or another cutoff. Passengers were required to be at the gate by 3:05pm; we didn �t get to the airport till 3, but there was no line at security, so we still made it in time.

For your specific question, either could apply depending on what you are trying to express. You can be on time, meaning you arrive at an appointed time to catch the train, or you can be in time, meaning you won �t be late, regardless of what the appointed time is.