You may remember that, back in July, Apple released rare bug-fix updates for older versions of its operating system: iOS 10.3.4 and iOS 9.3.6. This was necessary to help keep older iPhones and iPads maintain accurate location functionality as the GPS network goes through a time rollover transition.
Apple has started warning iPhone 5 owners with full-screen alerts that they’ll lose key online features (including email, web browsing, the App Store and iCloud) if they don’t update to iOS 10.3.4 before 12AM UTC on November 3rd. The GPS time rollover issue that started in April will throw off features that require the correct date and time, Apple said.
You’re not completely stuck if you can’t update to 10.3.4 before November 3rd, but you will have to backup and restore to a computer if you intend to move to the newer software. Other devices like the fourth-generation iPad are also affected, but they’re only expected to lose GPS functionality.
To update to the bug-fix release, simply go to Settings -> Software Update.