System of dating
As a continuous system of year enumeration the oldest era in practical use appears to have been that known as the "Era of the Martyrs" or "of Diocletian" () was in familiar use in Spain from the fifth century down to late in the Middle Ages.It adds about thirty-eight years to the ordinary numbering of the Christian Era.
On the other hand, the last three agree in using the Christian Era and from this time the practice is continuous.
In the intervening year which breaks this series into two parts falls the death of Bede A. 735." Very noteworthy is the decree of an English synod held in 816, wherein it is prescribed that the bishop shall put the acts of the synod into writing and date them by the Era of the Incarnation.
This points no doubt to a time "when ecclesiastics knew the era well enough but had not yet acquired the punctual habit of using it".
But even the bulls of such a pontiff as Innocent III are not unfrequently at fault, and as Léopold Delisle has shown, an erroneous calculation of the indiction may be perpetuated through a whole series of authentic documents (Bib. The point of main interest in this connection is to determine the source and period of the introduction of our present system of dating by the Christian Era.
Although, as explained in the article GENERAL CHRONOLOGY, the monk known as Dionysius Exiguus, when resident in Rome, c.