Thanks to scum-of-the-internet 4chan, we’ve all been hearing lately about a particular iOS bug that will brick modern iPhones, if you set the date back to 1/1/1970. Why does that happen? YouTuber Tom Scott explains.

Scott gives a quick lesson in Unix time to explain why he thinks the bricking happens: for your iPhone, time is displayed as one single integer, representing the number of seconds since 1970. If you set the time back to Jan 1st, 1970, that value becomes 0—not a problem in and of itself, but if the phone tries to display a time before that, say a text you received a few hours ago, it will generate a negative number, which causes a crash.

This is only a theory—Apple hasn’t confirmed what causes the bug, and probably never will. Even so, Scott’s video is worth watching, both as a lesson in how computers intrepret time, and a cautionary tale for programmers everywhere.

If you’ve bricked your phone, the good news is it isn’t gone forever: you need to either let the battery run entirely down (slow), pry the phone open and disconnect the battery (scary), or perform a Device Firmware Update (hard). Or, take it to an Apple Store, and ask them nicely not to laugh at you.