PC HELP!? 10 POINTZ!?

so at midnight i get logged off because of the time limit on the pc..so 15 min. before i get kicked off, in the bottom right corner it will say "you will be logged off in 15 minutes" so how can i cancel it for bypass it or something! i cant change time because i need admin pass for that so plz help me and give good answers with all detailed steps i really need help here! 10 points!