If you use an iPhone or iPad that was introduced in 2012 or earlier, you must check your device for an iOS update if you want it to continue to report the correct time, date, and location.
Apple is pushing one software update to a selection of older iOS phones and tablets to resolve a global GPS issue. The problem is known as the Week Number Rollover problem and the cause is due to GPS systems that register weeks as 10-bit digits. That means that when they hit week 1.024 (slightly less than 20 years), the count is reset and the result is that some older hardware is literally and literally thrown out of the race.
GPS makers such as TomTom and Garmin have been issuing patches for a while for this problem, and now Apple is doing the same. The earliest issue with the week number rollover on devices was April 6, but Apple says the hardware won't be affected until November 3.
Newer phones and tablets that work with the latest version of iOS (and have been updated!) Are already covered, but Apple is now extending that coverage to older devices.
The software update appears as iOS 10.3.4 for the iPhone 5 and the fourth generation iPad, and iOS 9.3.6 for the iPhone 4S, first generation iPad mini, iPad 2 and third generation iPad. Apple says the issue doesn't affect iPads with WiFi or the iPod touch alone.
You can read the full announcement from Apple here, with instructions for updating your phones and tablets. It may sound like an unnecessary hassle, but if you have made an effort to keep your old iPhone or iPad up and running, it is worth updating it to maintain this important functionality.