in time—
1. early enough for an activity; before it is too late to do smth.:
- I got there in time to see several friends I hadn’t seen in two months.
2. in the end; after a while:
- Ted and Jim did not like each other at first but in time they became close friends.
3. (Music) in the right rhythm:
- You need to play in tune, but what about playing in time? Rhythm is part of the musician’s trinity that also includes harmony and melody.
on time—
1. at a prearranged or scheduled time; punctually:
- The train, which was due at four o’clock, arrived exactly on time.
2. (U.S.) on the installment plan; on credit:
- Everything was bought “on time,” hardly any transactions involved cash.
Note: The expression is not equivalent in meaning to the phrase to time—in conformity with the scheduled time:
- The buses on this route seldom run to time.
See also: on the clock / on the hour.