In the 6th century BCE the Medes and Lydians were fighting near the Halys River in modern day Turkey. The Medes were fighting to avenge the murder of their king’s son. Hunters who were insulted by the king of the Medes for not brining back any food, killed his son and tricked the Medes into eating him. They then fled for the nearby Lydian empire who granted them asylum. As the battle raged on, a total solar eclipse occurred and stunned the soldiers and kings. The eclipse was taken as an omen and the two sides made peace.
This battle is considered to be the earliest historical event that we know the exact date for. Due to our ability to accurately predict solar eclipses, astronomers have determined that the battle occurred on May 28, 585 BCE.