What is the difference between on time and in time?
‘In time’ means to be at the edge of the specified time, with no spare time left.
‘On time’ means to be punctual, with spare time left.
To clarify that here are two examples:
I arrived just in time to catch the train. (So any later and you would have missed it).
I arrived at the station on time (So you had time to spare and spent some time actually waiting for the train).
In time is frequently used with the word ‘just’ as in our example above. See the British Corpus for more examples: http://www.natcorp.ox.ac.uk/