Moon Age, Solar Abnodal, and Eclipse

The Maya sometimes recorded how many days since the previous new moon a particular day fell on. They used slightly different calculations for this a different times, so the date shown in the program is only an approximation of what might be recorded by the Maya.

Based on the location of the moon in relation to the sun, on a given new moon, the moon can pass in front of the sun causing an eclipse. Due to the way the orbits work, this can only happen at certain points. A particular mathematical construct, called the Solar Abnodal, measures when this can happen. If there is a new moon in a period when the Solar Abnodal calculation is near zero, there is a high chance of there being an eclipse visible from the Maya region.