World Time by Utech 2.1.6

World Time by Utech is an easy to use utility that lets you place digital or analogue World Clocks onto your computer desktop. They will quietly tick away, ready for you when you need them. They even hide automatically and come back instantly as needed, no clicking required. To create clocks just move your mouse over the world map and discover the time and name of over 850 places around the globe. Click anywhere on the map or just start typing a name and you will instantly see the current time of that location on the world clock and create your desktop clocks on the fly.

If you want to find out when it is best to ring someone in a different time zone, just travel through time by turning on the "time wheel". The appearance of the clocks and their behavior is fully customizable to your personal preferences. You can even have a different clock color for night times.