Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
But these pleasantries had nothing to do with the stage(11) and with literature; they were performed by amateurs where and when they pleased, and the text was not written or at any rate was not published.
11. The close and original connection, which Livy in particular represents as subsisting between the Atellan farce and the -satura- with the drama thence developed, is not at all tenable. The difference between the -histrio- and the Atellan player was just about as great as is at present the difference between a professional actor and a man who goes to a masked ball; between the dramatic piece, which down to Terence's time had no masks, and the Atellan, which was essentially based on the character-mask, there subsisted an original distinction in no way to be effaced. The drama arose out of the flute-piece, which at first without any recitation was confined merely to song and dance, then acquired a text (-satura-), and lastly obtained through Andronicus a libretto borrowed from the Greek stage, in which the old flute-lays occupied nearly the place of the Greek chorus. This course of development nowhere in its earlier stages comes into contact with the farce, which was performed by amateurs.
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Reference address : https://www.ellopos.net/elpenor/rome/4-13-literature-art.asp?pg=20