The eclipse before Gaugamela

Eleven nights before Alexander met Darius at Gaugamela, the full moon was eclipsed over both armies, and a Babylonian scribe wrote it down.

The tablet is damaged but readable enough, and it is one of the anchors that lets ancient chronology be tied to real dates rather than reign lengths. Persian and Macedonian astrologers read the same event opposite ways; the one who read it as bad news for Darius happened to be right.