A bug has been discovered that causes some recent iOS devices to be permanently bricked if the user changes the date to January 1st, 1970, and reboots. So please, don't try this at home, although it's hard to understand why anyone would want to.
Some Reddit users have reported that a device will come back on after about 5 hours but can be very laggy. Others who have tried this hack noted that changing the SIM card or draining the battery sometimes fixes the problem, but most people are finding that a journey to the Apple store is their only option.
The most likely cause is thought to relate to the fact that many computers use January 1, 1970, as the epoch time - a reference point that devices count away from so they can work out the date.
Changing the clock to January 1, 1970, causes the device's internal clock to be set to less than zero, which confuses it and causes the crash.
Any iOS device sporting a 64-bit processor - A7, A8, A8X, A9 and A9X - and running iOS 8 or newer can be affected; this makes the iPhone 5S and later models susceptible.
We're waiting to see if Apple rolls out an update that fixes the problem, but the obvious way to avoid potentially bricking your device is not to set it to this date!
If you want to see just how the bug destroys an iPhone, check out the step-by-step video below.