UPDATE: Here's a fix (but it involves removing the battery).
All you have to do is set the date to 1 January 1970, and the device will no longer reboot.
Here's a video showing it in action (so you don't have to!).
ZDNet strongly suggests that you do not attempt this with your iOS device. Short of getting a replacement handset, there is no known fix for this.
There is also concern that devices accessing a public Wi-Fi could be maliciously bricked by a hacker setting up a rogue time server to broadcast the date as 1 January 1970.
The issue affects iPhones, iPads and iPod touch devices which have a 64-bit processor and which are running iOS 8 or iOS 9. This means that the following are affected:
- iPhone 5s and above
- iPad Air and above
- iPad mini 2
- Sixth generation (2015) iPod touch