Tertullian was not sure of this date; he wrote "for such is the assertion of Marcion" (C.M. 4/7) whereas he had previously retained (C.M. 1/15) in the twelfth year. It can therefore be considered that this date (which indicates the period from August 28 to August 29 of our era) is approximate.
Why did Marcion place a historical date at the beginning of his Gospel? This date would mark the descent of Christ a century before the manifestation of Marcion, which would then be around the year 129 AD; the information is interesting but it remains incomplete because we do not understand how a mythical event such as the descent of a god on earth, timeless event, could be dated, that is, become historical.
Only one explanation seems possible; this mythological fact could only be transposed into an episode of history when it was linked to the existence of a man who, according to the belief of the sect, would have witnessed it; the descent of Christ would not have been dated in the abstract, the date would mark the moment when a holy man would have thought to attend, receive a divine message, be the privileged witness and become the true missionary. We would thus have the date not of a fabulous episode but of the illumination of an ascetic, the beginning of his apostolate, the belief of his faithful.
The corrector of Luke took possession of this date and wanted to extend it with an imaginary historical context; he introduced in verse 3/1 the names of Pontius Pilate, Herod, Philip, Lysanias, Anne and Caiphas, John the son of Zechariah, details unknown to Mark and Matthew, but whose purpose was to transform a mythical event into a Jewish history, this connection or correspondence between myth and lived history being commonly felt by primitive peoples, simple people or mystics.
The insertion in Luke alone of these "historical" characters was to prepare their entry into the scene for later, at the moment when the Passion was added to the original text.
(my bold)In addition, we may suspect our narrator of having had an ulterior motive to substitute for the descent of Christ on earth the hearing of a heavenly voice by John the Baptist. "The word of God was addressed to John in the wilderness." But what was that voice saying and really talking to John? What is known about this is different; the celestial voice pronounced the famous phrase "You are my beloved son" but she addressed Christ (Luke 3:22).
Marcion's corrector used a stratagem to use in favor of John the Baptist a divine phenomenon that did not concern this "precursor" unknown to the primitive text.
In any case, Marcion would not have accepted this transposition of the central event of his gospel, nor this change of character. If the divine visit he had celebrated had taken place on that date and had been received by someone, it could only (apparently) be by the great apostle Paul whom he venerated and of which we know that he saw and heard Christ.
St. Paul announced that he had been "chosen by God from the mother's womb to carry his Son in him and preach his gospel" (Galatians 1/15); a phrase which could inspire a beautiful account of the nativity of Paul! He also said, "It is no longer I who live, but Christ lives in me" (Gen. 2:20). In his Epistle to the Philippians (1/20) he wrote "now as always Christ will be glorified in my body." He also confided to his adepts, "I know a man in Christ who is fourteen years old ... was delighted to the third heaven" (He Cor 12: 2), a sky that was precisely the sky of the good god and the Christ of Marcion. As Irenaeus says (III, 13, 1) "only Paul knew the truth because the mystery had been revealed to him by manifestation." Although the account of the Acts (22 / 6.11) was distorted by a Judaizing corrector (7), it testifies to a belief in the appearance of Christ on Paul on the road to Damascus. Let us not forget that, according to Esnik, Jesus chose St. Paul as human assistant, revealed the conditions of salvation and sent him to preach his gospel.
So the entire idea of an man adopted/possessed by God is only functional to the same function of a John the Baptist or of a Paul: to witness the descending of Jesus Christ in a precise date of the History.
The idea that Jesus descended on the Cosmos never seen by people or demons is very the oldest idea among all.
It was replaced by the idea of a first human witness: the man Jesus himself, distinct from Christ.
It was replaced by the idea of a first human witness distinct from both Christ and Jesus: John the Baptist, in clear opposition to Paul.