In time:
a) before the time by which it is necessary for something to be done.exp: Will you be able to finish it in time?
exp: just in time
On time:
> at the correct time or the time that was arranged.
exp: Jack was worried about whether he'd be able to get there on time.
Actually, 'in time' has another meaning as b) as below:
b) after a certain period of time, especially after a gradual process of change and development
exp: He wants to see changes in the company and I am sure he will, in time.
I think in this situation, the 'in time' means '假以時日'.
