Note that there is no discernable pattern or simple formula for knowing when an eclipse happened during a particular month and year, or to predict when the next total solar eclipse would happen in the same geographical location. In adition, bad weather further reduced the number of observable eclipses. Lunar eclipses follow after periods of 135 and 223 months. Plotting the distribution of months in the above table shows two peaks near 120 months and 270 months, but only half the total solar eclipses cluster near these two intervals. Astronomers using the 135-month or 223- month lunar eclipse periods to forecast total solar eclipses would be wrong at least half the time. Odds are similar to tossing a coin to predict whether an eclipse would occur this month.

Only after the lunar orbit was determined, and the changing orbital speeds of the Moon and Earth were established, could total solar eclipses be forecast to within the nearest month or less. This level of sophistication in astronomy was reached by Greek astronomers around the first century BC followed by Chinese astronomers centuries later. We can only speculate on the extent of knowledge lost in the fires of the Great Library at Alexandria, or in destruction by Spanish Conquistadores and missionaries in Mexico, Peru, and Chile.