This page describes how to divide a circle in 12 parts. You will see that this is very easy, in fact a lot easier than dividing a circle in 8 pieces. Presumably this is a mayor reason that we still now are dividing days in 12 hours, the sky in 12 zodiak-signs, and the circle in 360 degrees.

Step 1. Start out with a circle.

Step 2. Add another circle from the same size with its center on an arbitrary point of the other circle.

Step 3. Start the next circle on the intersection of the two

Step 4. continue doing this till you are round

Step 5. You will see the circle is divided in 12, in a very precice way. Note that you didn't have to change the size of the circle, which is very convinient when you have only a stick and a rope to use. Compare this with the division in 8.