ar winter solstice. The system of equations are examined to determine if a solution exists, if a solution doesn't exist or if N is greater than 100 million years, the equations are abandoned. Choose another set of U, A and other parameters and set up the equations for N again. The procedure is repeated until an acceptable solution for N is found.</p><br><subsect id="equations">Congruence Equations</subsect><p>Chinese almanacs usually took the winter solstice as the beginning of a year, even though most of t