This is a so-called Dockling, a tiny piece of code which spends its whole life living in the Dock. The purpose of Clockling, is to provide a more flexible alternative to the Clock application bundled by Apple in Mac OS X. For example, you can move this dockling to any part of the dock, you can customize the background and do other modifications using the minimal interface. It also leaves a smaller memory footprint than Clock does. Both analog and digital mode.