The section below refers to iOS 9.1, where there was a bug in updating your device overnight. From our experience this is no longer the case with the newer revision, iOS 9.3.
With iOS 9, Apple is trying to encourage more users to install the incremental updates that provide fixes and small improvements by offering the chance to install them for you overnight when you are sleeping. If you're prompted to update your iPhone while you're using it, Apple now lets you choose 'Later,' which will then specify a time period during which it will update automatically for you if you've got your iPhone plugged in to a power source, which most people do overnight anyway.
When Apple prompted Macworld's own Ashleigh Allsopp to update to iOS 9.1 and offered me that 'Later' option, she decided to make the most of the convenient new feature. She expected to wake up in the morning as usual to an updated iPhone. And indeed she did, but she woke up more than an hour after her alarm was scheduled to go off. The update had worked brilliantly, but her alarm had been deactivated, causing her to be very late for work.
She's not the only one. Users have taken to social media and forums to express their annoyance with the issue, which we consider to be a bug, and many have been late for important meetings and school.
Therefore, we'd only recommend choosing the later option if you don't have to wake up at a particular time in the morning, or if you can set another alarm on a different device!
How to update to iOS 9: The basics
iOS is the operating system software that runs on iPad, iPhone and iPod touch devices. It's the underlying framework that organises, launches and runs other apps, and can perform a number of features of its own. iOS 9 is the newest update to iOS, and launched officially to the public on 16 September 2015.
If you've got an iPhone 4s (or later), an iPad 2 (or later), either of the iPad mini models, or a fifth-gen iPod touch, your device is officially rated as iOS 9-compatible, and you can update to iOS 9 for free. (We discuss the list of compatible devices in a little more detail in the next section.)
We discuss iOS 9 as a single entity for most of this article, but we should quickly acknowledge that a number of smaller point upgrades will be released throughout its year-long lifetime, and some of those have already arrived. When you update your device to iOS 9 you will automatically get the most recent version that is available.
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