If you want the full clock in Gnome Shell, you can get it by doing the following steps:
Click the clock and go to Date and Time Settings.
After clicking Unlock at the bottom the left of the window, click on next to 24-hour time to change the clock to 12-hour time.
To add the full date to the clock, use dconf. To open it, press alt + f2 and run:
Go to org > gnome > shell > clock, and check the box to show date.
The clock will then have the full date, not just the day of the week.