With Niagara Launcher, you can change the clock widget at the top of your home screen.
It should be noted, that one can only have one custom widget displayed at once. Since we are making use of this feature you have a modified clock and display another widget at the same time.
- Go to the bottom of the all apps list > Niagara settings > Features > Niagara Widget > Add custom widget.
- After having chosen your widget, long press on it on your homescreen and tap on "Replace with widget".
- You can also make your own custom clock widget using the app KWGT for example.