This is an analog clock desklet for the Linux desktop environment Cinnamon (https://github.com/linuxmint/Cinnamon)
Copy the folder 'analog-clock@cobinja.de' to '$HOME/.local/share/cinnamon/desklets' or create a corresponding softlink. Then you can enable it via Cinnamon Settings.
The folder 'analog-clock@cobinja.de' contains a folder called 'themes'. You can put your own themes in there. Hint: Use the default theme as an example. Adjust the file metadata.json in your theme accordingly, pivot-x is usually half of the width on your clock pointers and pivot-y is the length from the center of the clock.