Note 74 — Chapter IV · PERSIAN OPERATIONS IN EUROPE: B.C. 493–490. MARATHON.
Reading edition
The Persian dead are still unburied when the Spartans visit the field. H. vi. 120. They leave Sparta on the 15th, and arrive at Athens on the 17th. A period of several days intervened between the arrival of the Athenians at Marathon and the battle.
Plutarch (De Herod. Malign. 26) asserts that the battle took place on the 6th of Boedromion. He accuses Herodotus of suppressing the fact that the Athenians held a festal procession in honour of the battle on the 6th of this month.
It is true that the festival did take place on this date; but the day was chosen, not because it was the date of the battle, but because it was the festival of Artemis Agrotera, to whom a vow had been made in case of success, probably before the army started from Athens.