In time = before you are late On time= punctual "in time" - there is a deadline. If we are past this deadline, we will miss the chance to do something. The show starts at 8 p.m. and no one is admitted after the show starts. I hope we will make it to the theater in time. "on time" - there is an expected time. We are meeting friends for dinner at 7 PM. I hope we will be on time and we don't make them wait for us.

On time usually refers to if something was scheduled and you got there on schedule, in time is usually used if something wasn't scheduled. For example, on time: Suppose an employee went to work and his boss told him to be there at 8:00 sharp, then he arrived at 8:00. The boss might say "You're right on time! Be early next time." in time: suppose there was this person who was drowning and his friend was there, but could do nothing about it because she was tied up to a tree, then another one of their friends came. The girl tied up to the tree might say, "John! You're just in time! Lucy's drowning, save her, then help me out of this tree quickly!" Understand?

on time 是准时的 ex; You must be come to school on time. in time 是及时的 ex:He informed me of this news in time.

in time: 及時 on time: 準時 Is it helpful to you to understand better?