Actiaca Aera was a computation of time from the battle of Actium.
They do not differ on any point of faith; the dispute is confined to a quarrel as to the correct chronological date for the computation of the era of Yazdegerd, the last king of the Sassanian dynasty, who was dethroned by the caliph Omar about A.D.
The date of the Nativity as fixed according to our common computation of Anni Domini (first put forward by Dionysius Exiguus at Rome early in the 6th century) has long been recognized to be too late.
As frequent allusion is made by classical writers to this embarrassing method of computation, which is carefully retained in the ecclesiastical calendar, we here give a table showing the correspondence of the Roman months with those of modern Europe.
It Is Therefore Infinitely More Commodious To Determine The Commencement Of The Year By A Fixed Rule Of Intercalation; And Of The Various Methods Which Might Be Employed, No One, Perhaps Is On The Whole More Easy Of Application, Or Better Adapted For The Purpose Of Computation, Than The Gregorian Now In Use.