Reboot your phone. If that doesn't work, install the official "SIM Toolkit" app from the link below and reboot again.
https://www.apkmirror.com/apk/googl...lease/sim-toolkit-8-1-0-android-apk-download/
---------- Post added at 11:38 AM ---------- Previous post was at 11:37 AM ----------
Clicking on the default date widget ("Thursday, Aug. 30") starts a toast with "App isn't installed". Shouldn't this open the clock app, so I can easly setup alarms?
Try installing the Google "Clock" app from the Google Play Store.