In time vs. on time

Test No. [color=blue]errors/inter-15 “Sleep well”, question 3

Nevertheless she made every effort to get to work on time to open the shop before customers arrived.

(a) Nevertheless
(b) on
© before

Test No. [color=blue]errors/inter-15 “Sleep well”, answer 3

Nevertheless she made every effort to get to work in time to open the shop before customers arrived.

Correct entry: in
The error was: (b) on

You have [color=red]not found the error.
Nevertheless she made every effort to get to work on time to open the shop before customers arrived.
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Is there any difference between: in time and on time?

On time means punctual as in: In Switzerland the trains always arrive on time (they are never late). In time means with enough time to do what you want to do. So we could say: You must arrive in time at the station if you want to catch that train because the trains always arrive on time.