2 There is also another solution of this question, that we should not here understand the sixth hour of the day, because John says not, And it was about the sixth hour of the day, or about the sixth hour, but says, “And it was the parasceve of the passover, about the sixth hour”. And parasceve is in Latin præparatio (preparation); but the Jews are fonder of using the Greek words in observances of this sort, even those of them who speak Latin rather than Greek.
It was therefore the preparation of the passover. But “our passover, Christ,” as the apostle says, “has been sacrificed;” and if we reckon the preparation of this passover from the ninth hour of the night (for then the chief priests seem to have given their verdict for the sacrifice of the Lord, when they said, “He is guilty of death,” and when the hearing of His case was still proceeding in the high priest's house: whence there is a kind of harmony in understanding that therewith began the preparation of the true passover, whose shadow was the passover of the Jews, that is, of the sacrificing of Christ, when the priests gave their sentence that He was to be sacrificed), certainly from that hour of the night, which is conjectured to have been then the ninth, on to the third hour of the day, when the evangelist Mark testifies that Christ was crucified, there are six hours, three of the night, and three of the day.
Hence in the case of this parasceve of the passover, that is, the preparation of the sacrifice of Christ, which began with the ninth hour of the night, it was about the sixth hour; that is to say, the fifth hour was completed, and the sixth had already begun to run, when Pilate ascended the tribunal: for that same preparation, which had begun with the ninth hour of the night, still continued till the sacrifice of Christ, which was the event in course of preparation, was completed, which took place at the third hour, according to Mark, not of the preparation, but of the day; while it was also the sixth hour, not of the day, but of the preparation, by reckoning, of course, six hours from the ninth hour of the night to the third of the day.
Of these two solutions of this difficult question let each choose the one that pleases him. But one will judge better what to choose who reads the very elaborate discussions on “The Harmony of the Evangelists.” And if other solutions of it can also be found, the stability of gospel truth will have a more cumulative defense against the calumnies of unbelieving and profane vanity. And now, after these brief discussions, let us return to the narrative of the evangelist John.
Source: Tractates on the Gospel of John (New Advent)