Force the user to logout when timer sets to 0

I have Master page there i am passing the Session value

what i want is when the user login , i have set the timer 10.00 ie: 10 hours

so user will be able to access his account totally on 10.00 hours if he

Logout inbetween the 10 hours the remaining time will be stored in database

so once he relogin - the countdown time starts from the remaining time in the

Database. and also if the user login so he has only 5 Mins more to expire

After the 5 Mins i have to force the user to logout how ??
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