23. 18 into 747

A tablet found in the 19th century provided the first hint that Babylonian astronomers were familiar with the Saros. Now known as the Saros Tablet, it lists the years 7 Nabonidus, 8 Cyrus, and so on into Seleucid times. Next to each entry is written the number 18, and the entries are in fact 18 years apart.

Initial attempts to fit a Saros cycle to the list of years were inconclusive, but an intriguing discovery emerged when the list was extrapolated back in time. Backtracking 11 intervals of 18 years from the initial entry (-548) brings the date to Nabonassar 1 (-548-11x18=-746).