When Does "The Persians" (472 BCE) Take Place?

"Pérsai" (released to English-speaking audiences as "The Persians") is a historical fiction stageplay written by Aeschylus first performed March 472 BCE. So when is "The Persians" set? 

It takes place in the year: 

480 BC 

We know this because the real-world Persian King Xerxes I (518 BCE-465 BCE) appears and he passed in August of 465 BC. He is immediately referred to by the Chorus as "our Lord and King, / Xerxes, Darius-born"... so he is definitely Xerxes I, son of Darius the Great (550 BCE-486 BCE) and not Xerxes II (unknown-424 BCE), son of Artaxerxes I (unknown-424 BCE), and it must be before August of 465 BC. 

More specifically, the real-world Persian King Darius the Great (550 BCE-486 BCE) also appears but as a ghost. The real-world Persian Empress Atossa (550 BCE-475 BCE) says, ..."calling from his grave / Darius, the Great Spirit, to rise and save, / While I, the Queen, in due procession go / With draughts earth-slaking to the Gods below." Since he passed in October of 486 BC it must be after October of 486 BC. 

Specifically, a messenger brings recent news saying, ..."in one blow our garnered bliss is fled, / All, and the flower of Persia fallen and dead!" then "The whole host / Of Barbary, O my countrymen, is lost!" and, finally, "Crowded with dead men miserably lost / Is Salamis, and the bay, and all the coast." The real-world Battle of Salamis was fought between an alliance of Greek city-states and the First Persian Empire on September 26th, 480 BC or September 27th, 480 BC during the Second Persian War. Xerxes arrives retreating from the battle with most of his army not long after the messenger arrives. So it is late September of 480 BC or maybe early October of 480 BC. 

It was adapted to film in 1961, then to film again in 1975, and a final time in 2020.