This must be Thursday. I never could get hang of Thursdays. --Arthur Dent in The Hitchhiker's Guide to the Galaxy.
In Asimov's Chronology of the World I read about an ancient battle interrupted by a solar eclipse. While most ancient dates are estimates, Asimov remarks that modern astronomers can date the eclipse and thus the battle to the exact date of 28th May 585 B.C. Let's assume this to be accurate.
Today is a Friday. Yesterday was a Thursday. Assuming this pattern goes back, what day of the week was the battle?
More information about the Battle of the Eclipse from wired.com (non-comtemporary publication):
May 28, 585 B.C: A solar eclipse in Asia Minor brings an abrupt halt to a battle, as the warring armies lay down their arms and declare a truce.
Aylattes, the king of Lydia, was battling Cyaxares, king of the Medes, probably near the River Halys in what is now central Turkey. The heavens darkened. Soldiers of both kings put down their weapons. The battle was over. And so was the war. After 15 years of back-and-forth fighting between the Medes and the Lydians, the kings of Cilicia and Babylon intervened and negotiated a treaty. The River Halys, where the Battle of the Eclipse was fought, became the border between the Lydians and the Medes.
The most likely candidate for the eclipse took place on May 28, 585 B.C., though some authorities believe it may have been 25 years earlier in 610 B.C.