This is an analog clock desklet for the Linux desktop environment Cinnamon (https://github.com/linuxmint/Cinnamon)
Copy the folder '[email protected]' to '$HOME/.local/share/cinnamon/desklets' or create a corresponding softlink. Then you can enable it via Cinnamon Settings.
The folder '[email protected]' contains a folder called 'themes'. You can put your own themes in there. Hint: Use the default theme as an example.