The recent changes to Windows Phone in the form of WP8.1 mean that live tiles are no longer restricted to updating every 30 minutes but can now update every one minute. This means the tiles can contain a usable clock. Developers quickly took advantage of this and there were a couple of live tile digital clocks soon appeared.
Now a very nice looking analog clock has hit the market and it's available in the Windows Phone store here…
There's plenty of clocks already on WP8... the Glance screen, the lock screen, and in the status bar at the top of the screen. Sometimes though just for esthetic looks you might want one on the start screen.

Windows Phone