1970 bug
So as many I did the January 1st 1970 date on my iPhone 6s and I now see everyone saying apple replacing it for them but I'm not sure if I have a warranty or not. If I don't have it am i ******
iPhone 6s, iOS 9.2
Put the phone in DFU mode:
http://www.payetteforward.com/how-to-put-iphone-dfu-mode/
You will then have to reload all of your data from your back up.