Notation and other clocks. To avoid continually explaining that you are working with regular integers, or on a 12-hour clock, there is a notation for writing equations. Actually, you should use an equals sign with 3 bars instead of 2, but this part of this page is still under construction. There is no reason to stick with 12-hour clocks. The same principles work with any positive whole number of hours.
Some clocks are especially interesting.
About the 10-hour clock. About the 9-hour clock. About the 11-hour clock. About the 2-hour clock. Source code for the java applet.