If you see someone on a forum or elsewhere online suggesting setting your iPhone’s clock back to the ’70s, under no circumstances should you follow through with it.
iPhone users have discovered a bug that could permanently brick your phone. Setting your phone to its earliest possible date, January 1, 1970, causes the crash. Apple hasn’t released an official statement regarding why this is happening.
However, CNN Money speculates it has to do with Unix time. Unix began counting seconds at midnight on January 1, 1970, GMT, making the date 00:00:00 in Unix time.