Apple has acknowledged the existence of the date bug that can brick iOS devices.
Apple's comment is short and sweet:
If you changed the date to May 1970 or earlier and can't restart your iPhone, iPad, or iPod touch
Manually changing the date to May 1970 or earlier can prevent your iOS device from turning on after a restart.
An upcoming software update will prevent this issue from affecting iOS devices. If you have this issue, contact Apple Support.
The bug is strange but very effective. All you have to do is set the date to 1 January 1970, and the device will no longer reboot.
Over the weekend a fix emerged, but this entailed removing the battery.
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
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