Saturday 3rd December 2016
I recently encountered a very strange bug while using an iPhone 4 running iOS 7.1.2 (the latest that it supports). The phone had been acting strangely for a long time, with many little quirks, bizarre behaviour and some features simply not working.
The first thing that I noticed was that the alarm clock was very intermittent, sometimes sounding at the expected time (from the phone's perspective) and sometimes not at all. Also, the notification center was not showing my scheduled alarms like it is supposed to. Next, I noticed that the phone had no signal, but it actually did. The signal bar at the top left of the phone was not displaying an accurate status. It would say "No Service" most of the time, but the phone was sometimes still able to receive calls and text messages.
The system clock was running roughly 3 minutes behind the real time, possibly caused by the phone having not been connected to the internet for well over a year. I connected to the internet and toggled the "Set Time Automatically" option on and off in order to trigger a time synchronization. The clock set itself correctly and the phone started working completely normally. All issues were fixed.
All strange behaviour that I experienced:
I have tried reproducing these issues by disabling the "Set Time Automatically" option and deliberately setting the system clock incorrectly, but the phone continued working as normal. Perhaps this behaviour was a result of a prolonged time with the system clock set incorrectly. At least now I have documented this, and it may be useful to someone else in the future.