Augustine of Hippo — as excerpted in the Catena Aurea on John 19:12-16

“(Tract. cxvii) Why then doth Mark say, And it was the third hour, and they crucified Him? (Mark 15:25) Because on the third hour our Lord was crucified by the tongues of the Jews, on the sixth by the hands of the soldiers. So that we must understand that the fifth hour was passed, and the sixth began, when Pilate sat down on the judgment seat, (about the sixth hour, John says,) and that the crucifixion, and all that took place in connexion with it, filled up the rest of the hour, from which time up to the ninth hour there was darkness, according to Matthew, Mark, and Luke. But since the Jews tried to transfer the guilt of putting Christ to death from themselves to the Romans, i. e. to Pilate and his soldiers, Mark, omitting to mention the hour at which He was crucified by the soldiers, has expressly recorded the third hour; in order that it might be evident that not only the soldiers who crucified Jesus on the sixth hour, but the Jews who cried out for His death at the third, were His crucifiers. There is another way of solving this difficulty, viz. that the sixth hour here does not mean the sixth hour of the day; as John does not say, It was about the sixth hour of the day, but, It was the preparation of the passover, and about the sixth hour. Parasceve means in Latin, præparatio. For Christ our passover, as saith the Apostle, is sacrificed for us. The preparation for which passover, counting from the ninth hour of the night, which seems to have been the hour at which the chief priests pronounced upon our Lord’s sacrifice, saying, He is guilty of death, between it and the third hour of the day, when He was crucified, according to Mark, is an interval of six hours, three of the night and three of the day.”