It adds about thirty-eight years to the ordinary numbering of the Christian Era.
Where Byzantine influences prevailed the years were generally numbered from the beginning of the world ().
In the case of the popes we do not know any instance earlier than 787.
527, seems to have been the first to initiate the practice of calculating years from the birth of Christ and although it was undoubtedly he who identified the year of Christ's birth with the year 753 of the foundation of Rome, as is still done in our current chronology, nevertheless it was not until long after the age of Dionysius Exiguus that the system came into common use.The principle that imperial decrees and charters must be "dated" as a condition of validity, i.e.that they must bear upon them the indication of the day and year when they were delivered, may be traced back to the time of Constantine.In the official acts of most of the countries of Christendom, and notably in England, the regnal year of the sovereign was always given and sometimes this was the only indication of the year.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.
Concurrently with the year of the indiction it was customary both in papal and imperial documents to mention the regnal year of the pope or emperor.