Why is the day of the week missing?

Solution 1:

It's probably a bug in this update, which landed in focal-updates on 2021-03-25.

Please feel free to file a bug report:

ubuntu-bug gnome-shell

Solution 2:

I recently moved to 20.04 and had the same issue. One workaround I found was to open the Settings, disable auto update of the date if enabled, manually move the date a day forward or back in Settings, then while keeping the Settings open, open the top bar calendar and you should see the day-of-week appear. At that point just set the date back to the correct date or auto update in Settings and close. I couldn't tell you why this works though.