This program is a clock that shows which portion of the Earth's surface is illuminated by the sun. It is designed to be usually iconic, but can be opened for a larger display with the time updated every second and both the local time zone and UTC displayed. The Suntools version had a menu that allowed you to speed up time, show different dates, etc., but I have never implemented any of that in the X version; there is some support for it in the code, however.