Unfortunately, Clock has stopped.
The alarm clock (app) did not ring. I started checking why after waking up a bit late. Clicked the Clock icon and it just briefly popped up the "Unfortunately, Clock has stopped." message without even giving me a chance to [Report] or [OK] it. Clicked the Clock again. Same thing. Clearly the Clock app was crashing and despite numerous attempts I could not make it run. What do you do? Reboot of course. It always helps. This time it did not. Same thing. Unfortunately, Clock has stopped. I solved the problem by going to the [Apps] settings and cleared the application data. Clearly the data was corrupt and the app was crashing trying to parse it. We live with such crashes. But some apps should just never, ever do that. Clock is one of them. You cannot manually fix an app that is supposed to be your watchdog. Because then is just fails to be that watchdog. It will not wake you up and you will miss your important flight / meeting / wedding / (insert your own). This is a fai