Recently upgraded from Ubuntu 16.04 to 18.04. As I have been setting up my GNOME desktop, I changed my clock to a 12-hour format (AM/PM) in System Settings. However, my login screen still shows the time in 24-hour format.
Overall I have had a lot of trouble trying to configure the GDM shell of the login screen. Many old posts regarding management of things like background, appearance, and behavior seem outdated and don't work. Additionally, having upgraded (instead of a clean install) I can't browse my files to find any obvious configuration file to edit. Gnome Tweak Tool can't seem to manage anything related to the login screen either.
Any suggestions on how I can change settings and configure the GDM login screen environment on 18.04?