Maya astronomers calculated the length of the solar year to within roughly 17 seconds of the figure we use today, using no telescopes, no clocks, and no instruments Europeans would have recognised as scientific

The number everyone quotesMost versions of this story cite a Maya solar year of 365.2420 days. For comparison, the Gregorian calendar drawn up in 1582 runs on 365.2425 days, a slightly larger miss in the opposite direction. The figure is a reconstruction, assembled from the arithmetic the Maya left behind on their monuments, first by a chemical engineer with an unlikely sideline. Copán settled on 149 lunar months equalling 4,400 days, which works out to 29.53020 days per month. And the whole table runs 37,960 days for a reason: that figure divides cleanly by 584, by 260 and by 365.