If you’ve managed to hold on to your 2012-era iPhone 5 until now, you should probably update it before November 3rd.
You’ll need to update to iOS 10.3.4 in order to keep important functions including the App Store, iCloud, email, and web browsing working, according to Apple. If you’re not sure which version you’re running, Apple has a support page about the issue, which also explains how to check which version you’re using.
Your phone needs the update because of the GPS time rollover issue. Basically, GPS devices measure date and time using a week counter, which is only able to count up to week 1,024, after which the counter resets back to zero. Since GPS requires accurate time data to function, the reset can disrupt location data, too….