It would greatly assist the elucidation of this word, if the earliest instances extant of its use, in a chronological sense, could be ascertained.
The dictionary of Facciolatus goes no further back than Isidorus the younger, at the end of the sixth century; who perhaps was the first who gave to era the meaning of a cursus of years: before his time, as well as afterwards, it is certain that era was a synonyme of annus.
In recording dates, the Spanish account made no use of annus either expressed or understood—era was an independent word, having numerals in concord with itself: thus it was prima era, secunda era, tertia era, &c. Spelman therefore had sufficient reason to contend that the origin of era might be Gothic and not Roman, and that it is but a variation of our own word year. He says that Isidorus, when dating from the Roman epoch, used the Roman word, but that when dating from the Gothic epoch, he conformed to the idiom of the Goths, "apud quos," he adds, "eram annum significasse ex eo liqueat, quod prisci Saxones (quibus magna Gothis sermonis affinitas) annum 'Ȝear' dicebant—Angli hodie 'year'—Belgi 'iaer.'"
The absence of the diphthong in era is attributed by Facciolatus to the barbarism of the age; but it is at least equally probable that the diphthong never did really belong to era, but that its claim to it originated in the fanciful derivation from æs, as imagined by Isidorus—or rather from es, as he would spell it, the real corruption being in the latter word: thus, when the diphthong was restored to æs, it would, as a matter of course, be also applied to its supposed affinitive.
The Spaniards, who have the best right to the word, have never adopted the diphthong. With them it is still era, and Scaliger asserts that there is not in all Spain a single inscription in which the diphthong is recognised. Alluding to Sepulveda, he says,—
"Mirum mihi visum hominem doctissimum ac præterea Hispanum, cum tot monimenta extent in Hispania in quibus hujus rei memoria sculpta est, ne unum vidisse—In illis, ut diximus, nunquam æra, semper era, scriptum est."
The practical institution of the Spanish, or era account, was probably, like the Dionysian, long subsequent to its nominal commencement; so that an enquiry into its earliest known record would possess the additional interest of determining whether such were the case or not.
Censorinus, in his comparative enumeration of the various accounts of years—the Julian—the Augustan—the Olympiad—and the Palilian, makes no mention of the Era, which he would scarcely have omitted, had it been then in existence and of imperial institution. Between his time, therefore, which was towards the middle of the third century, and that of Isidorus, the practice of computation by eras most probably arose.
As for its institution by Cæsar Augustus, which rests on the authority of Isidorus; that suggestion, even if free from anachronism, had probably no better foundation than an accidental similitude in sound, and a wish to compliment the bishop of CÆSARAUGUSTA, to whom the epistle containing it was addressed by him of Hispalis. The latter appears to have dealt largely in conjecture in framing his Origines—as, for example, in hora,—
"Hora enim finis est temporis sic et oræ, sunt fines maris, fluminorum, et vestimentorum"—