12. Double dating

One Babylonian eclipse quoted in the Almagest is also known directly from a cuneiform tablet. The date inscribed on the tablet is Cambyses Year VII Month IV (Duzu), night of the 14th; the Almagest writes 7th year of Kambyses, which is the 225th year from Nabonassar, Phamenoth 17/18.

Modern computation agrees with the Cambyses tablet and the Almagest about the date of the eclipse, -522 July 17, but not much else. The three descriptions of the eclipse - Ptolemy's report in the Almagest, the account inscribed on the tablet and the computed one - do not match.