Apple is warning users of older iPhones they need to update their devices urgently, or it might stop working properly.
People with elderly models such as the Phone 5 or iPhone 4S need to install the latest software by 1pm on Sunday (NZ time) or face the major loss of key functions.
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The problem is caused by a roll-over in the GPS time system, which happens around every 20 years. After the roll-over, programs which use the GPS system for their date, time and location could be impacted.
"If you have an iPhone 5, it's especially important to update your device's software wirelessly or using your computer before November 3 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," Apple wrote on its website.
According to Apple, the affected models are the iPhone 5, iPhone 4S, iPad mini, iPad 2, and iPad 3rd generation.
If you've missed the deadline, 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.