How To Track The Time Left In Database

When a student taking a quiz having a duration of 2 hrs, a timer will start and keep track the time.

So if he logout or close the window, the remaining time should be recorded into the database. And when he take the same quiz again, the timer will not restart but continue from the previous time.

E.g i take a quiz having a duration of 60mins, and when i logout the time duration remain is 30mins. And when i logon and take the quiz again, the timer countdown from there 30mins but not begining of 60mins.