I set my iOS device to January 1, 1970...

UPDATED to include Apple Store services.

UPDATED to include the fact that iOS 9.3 fixes it

If you do this your phone will stop working, and not respond to any of the usual troubleshooting steps, such as a reboot a reset or restoring iOS. We're not sure why it happens, but it's related to the fact that iOS is a Unix based system, and Unix time starts at 0:0:0 UTC on January 1, 1970. All time is saved as seconds since that date-time, and converted as needed for human understanding. (Negative seconds refers to time before that date and time, and works back to 1904, but apparently Apple didn't include earlier dates because they didn't think you would ever take your iPhone with you in a time machine.) right now all you need to know is how to make the phone usable again.

If you upgrade your iOS device to iOS 9.3 using iTunes on your computer it will fix the issue.

After that, the best and easiest way to fix this problem is to take the phone to the Genius Bar at an Apple Store, where they can fix it in a few minutes by disconnecting the battery for a few seconds (don't try this at home, however). Be sure to make an appointment first to avoid a long wait.

https://support.apple.com/en-us/HT205248

<Edited by Host>