Rickh,

its not so much complicated as your are making it, first remember following things

its just a timein and timeout recording page, so

 you dont have to store sessions

when an employee or student comes he puch his card or thumb or what ever method your are using

your application will read his id and make an entry in attendance table,

when same card will punch again you have to upate the attendance table timeout field.

To implement this you have to make a check in your application programing that whenever a card is punched then check wheather there is any record in attendance table with the same id exists and timout field is empty then mark timeout otherwise mark timein

I think this will clear a logic for you to record timein and timeout, and not using the sessions.