Heidegger's Bible Handbook: 2 John: Time of Writing
4. The time of writing.
It is hardly able to be doubted that this Epistle was written in the precipitous decline of old age. For, for no better reason does it appear that Saint John calls himself the πρεσβύτερον/elder in the Inscription, than that he, being very old, and with his Apostolic office almost fulfilled, wrote the Epistle. Nevertheless, the time of writing is not able to be defined with certainty.