Released in September of 2012, the iPhone 5 isn’t what you’d call a “fresh” device, being more than 7 years old. Still, Apple is supporting it, up to a certain degree. Its latest support document is proof of that. Apple is warning iPhone 5 users to update their iOS, or else, risk losing important functionalities on their phones.
Starting just before 12:00 a.m. UTC on November 3, 2019,* iPhone 5 will require an iOS update to maintain accurate GPS location and to continue to use functions that rely on correct date and time including App Store, iCloud, email, and web browsing. This is due to the GPS time rollover issue that began affecting GPS-enabled products from other manufacturers on April 6, 2019. Affected Apple devices are not impacted until just before 12:00 a.m. UTC on November 3, 2019 — Apple
If you want to keep getting accurate GPS location, and continuing to use functions that rely on correct date and time including App Store, iCloud, email, and web browsing, you should update until November 3. If you won’t apply the update until then, “you will be required to back up and restore using a Mac or PC in order to update because over-the-air software updates and iCloud Backup will not work“, says Apple.