auto date and time incorrect iPhone

my iphone 4 decided to go bonkers this afternoon by changing its time and date while i was in class. the time is off by roughly 3.5 hours but whats worst is the date. its 11 april today but it states 17 april. i had to turn off the auto date and time to manually put in the correct date and time. tried restoring my phone but that didnt solve the problem either.
anyone knows what i should do?
iOS 4