From Duality Software:
DS Clock (64-bit) is a digital desktop clock that displays variable date, time, and time zone information built from the format string. The program allows you to fully customize its look and feel, and can synchronize your computer's clock with Atomic Time Servers. You can select any combination of date, time, and time zone, pick custom colors and fonts, set custom sound to play at the top of the hour, etc. DS Clock also allows you to show a tool tip window with upcoming reminders of Calendarscope and supports Swatch Internet Time and Stopwatches. Real Westminster chimes are available.