Exalauno Day is March 4th; a pun on the Greek verb 'exalauno' meaning "March forth", recurrently used in Xenophon's "Anabasis of Cyrus", (often translated as The March Upcountry or the March of the Ten Thousand).
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Xenophon's story is quite true, about the long escape of ten thousand Greek mercenaries from the heart of Persia after their leader, a claimant to the Persian throne, was killed. Took place in the generation before Alexandert the Great.
I read it a few years back after a respected acquaintance described it as 'the greatest true adventure story ever written'. It qualifies, and it is not a hard read.
Roxbury Latin School invented the holiday a century or so ago, and it makes the news now and then....