Owners of Apple products have been warned against manually setting the date on their device to 1 January 1970 - or being tricked by friends into doing it.
A bug within the products will cause them to get permanently stuck while trying to boot back up if the device is switched off.
It causes such an issue that users are reporting that not even the fail-safe restore techniques using iTunes can't repair the problem.
The date bug affects iPhones, iPads and iPod touches with 64-bit processors running iOS 8 or iOS 9, including the iPhone 5S onwards, the iPad Air, iPad mini 2 or the 2015 sixth-generation iPod touch or newer.
The precise cause of the problem is not known - although the way iOS stores date and time formats means that 1 January 1970 is stored as a value of 0 or less, causing every other process that requires the time stamp to fail.
Users curious about the bug have reportedly 'bricked' their devices trying to disprove the reports, ending up having to have them replaced by Apple.