Today the 27th December is the commemoration and feast day of Saint John. The Roman Catholic Church calls him “Saint John, Apostle and Evangelist”, and in the Anglican Communion, which calls him “John, Apostle and Evangelist”. In the Tridentine Calendar he was commemorated also on each of the following days up to and including 3 January.

From wikipedia

St John the Evangelist, painting by Jacopo Pontormo 1525

John the Evangelist (יוחנן Standard Hebrew Yoḥanan, Tiberian Hebrew Yôḥānān meaning “Yahweh is gracious”, Greek: Εὐαγγελιστής Ἰωάννης) (c. AD 1 – c. 100) is the conventional name for the author of the Gospel of John. Traditionally he has been identified with the author of the other Johannine works in the New Testament—the three Epistles of John and the Book of Revelation, written by a John of Patmos—as well as with John the Apostle and the Beloved Disciple mentioned in the Gospel of John. However, at least some of these connections have been debated since about 200.

The Gospel of John refers to an unnamed “Beloved Disciple” of Jesus who bore witness to the gospel’s message.The composer of the Gospel of John seemed interested in maintaining the internal anonymity of the author’s identity.
The apostle John was a historical figure, one of the “pillars” of the Jerusalem church after Jesus’ death.Some scholars believe that John was martyred along with his brother (Acts 12:1-2), although many other scholars doubt this. Harris believes that the tradition that John lived to old age in Ephesus developed in the late 2nd century, although the tradition does appear in the last chapter of the gospel, though this debatable tradition assumes that John the Evangelist, John the Apostle, the Beloved Disciple mentioned in John 21 and sometimes also John the Presbyter are the same person.

Of the other New-Testament writings, it is only from the three Epistles of John and the Apocalypse that anything further is learned concerning the person of the Apostle. We may be permitted here to take as proven the unity of the author of these three writings handed down under the name of John and his identity with the Evangelist. Both the Epistles and the Apocalypse, however, presuppose that their author John belonged to the multitude of personal eyewitnesses of the life and work of Christ (cf. especially 1 John 1:1-5; 4:14), that he had lived for a long time in Asia Minor, was thoroughly acquainted with the conditions existing in the various Christian communities there, and that he had a position of authority recognized by all Christian communities as leader of this part of the Church. Moreover, the Apocalypse tells us that its author was on the  scenic island of Patmos a small Greek island in the Aegean Sea and one of the northernmost islands of the Dodecanese group. John was there waiting “for the word of God and for the testimony of Jesus”, when he was honoured with the heavenly Revelation contained in the Apocalypse (Revelation 1:9).

The Coptic church states that St. John the Evangelist lived over 90 years, and they used to carry him to the gatherings of the believers. Because of his old age, he only gave very short sermons saying, “My children love one another.” It states that he wrote the gospel known after him, the Book of Revelation, and the three epistles ascribed to him. It confirms that he did not suffer martyrdom and died of old age in Ephesus,near present-day Selçuk, Izmir Province, Turkey.

Beloved, let us love one another: for love is of God; and every one that loveth is born of God, and knoweth God. He that loveth not, knoweth not God; for God is love.
– St John