Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon LXXXIX

Canon LXXXIX.  (Greek xcii.)

That bishops who are ordained shall receive letters from their ordainers bearing the date and the name of the consul.

It further seemed good that whoever thereafter should be ordained by the bishops throughout the African provinces, should receive from their ordainers letters, written in their own hands, containing the name of the consul and the date, that no altercation might arise concerning which were ordained first and which afterwards.

Notes.

Ancient Epitome of Canon LXXXIX.

Whoever is ordained in Africa let him have letters signed by the proper hand of him that ordained him, containing the date and the name of the Consul.

This is Canon iij. of Milevis, a.d. 402.

Johnson.

It is evident from this canon that the church in this age followed the date of the civil government, which was in the consulship of Caius and Titius, as our civil date is in the 1st, 2d, 3d, etc., year of the reign of our King or Queen.