December 2 isn't turning out to be a happy day for some iPhone users running iOS 11. Apple's mobile operating system has a bug where local notifications will cause your phone to crash.
Local notifications are ones that originate on your phone itself — like a reminder, for example. Under this current iOS 11 bug, local notifications appearing on Dec. 2 trigger a soft reboot where your iPhone crashes and restarts.
Apple already has a fix available in the form of iOS 11.2. If local notifications are bringing down your iPhone, you should download and install the update immediately.
To get the iOS 11.2 update, open your Settings app and scroll down to General. Tap Software Update, and the 11.2 update should be there waiting for you. Tap Download and Install, agree to Apple's terms, and follow any additional onscreen prompts. The update will install, and your restart problems should be a thing of the past.
Before downloading the update, however, you may have to follow Apple's recommended workaround for unexpected iPhone starts triggered by the local notifications bug. Why? Because any notifications you get while updating your software will cause your phone to restart.
I experienced this first-hand while upgrading my wife's iPhone 5s to iOS 11.2. She uses a meditation and mindfulness app that sends local notifications reminding her to keep calm and carry on — which was sending her phone into a decidedly not-calming cycle of restarts.
To disable notifications, go into Settings, select Notifications, and then tap any app that may be sending you local notifications to turn those off. Since you may not be sure which apps those are, you may want to play it safe by turning off any notifications until you've had a chance to update — at least if you don't have a lot of apps on your phone. Is this a pain? Oh my, yes.
There are other reasons to get iOS 11.2, other than the fact that it restores functionality to your iPhone. The update also introduces the ability to send money to your friends and family with Apple Pay in the Messages app. That feature will be fully enabled later on.