On Time or In Time

Just read friend's status at her facebook. She asked about the usage of "on time" term.

It is used for exactly at the time or before the time.

As I had studied English Idioms, I know that "On time" is for exactly at the time, then "In time" is for before the time. I commented the status and wrote what I know.

Need some reference, so I googled it. I got the "on time" meaning, it means not to be late; "in time" means before it is too late.
Now, I'm bit confused..
Is

before it is too late

have same meaning with

before the time

Well, I need some input here, please help me :D

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