Here are the relevant texts (from the NASB):
Now it was the day of preparation for the Passover; it was about the sixth hour. And he said to the Jews, "Behold, your King!"
It was the third hour when they crucified Him.
Sometimes, hand-written copies of the same document will not entirely agree with each other. Copies of the Bible are not immune from this. This verse in John is a case in point.
Peter, Bishop of Alexandria, around 300 AD, makes the following statement in a manuscript fragment entitled "That Up to the Time of the Destruction of Jerusalem, the Jews Rightly Appointed the Fourteenth Day of the First Lunar Month" regarding this text in John 19:14:
"...'And it was the preparation of the passover, and about the third hour', as the correct books render it, and the copy itself that was written by the hand of the evangelist, which, by the divine grace, has been preserved in the most holy church of Ephesus, and is there adored by the faithful."
According to Methodist commentator Adam Clarke (1760 - 1832):
"trith, the third, is the reading of DL, four others, the Chron. Alex., Seuerus Antiochen., Ammonius, with others mentioned by Theophylact.
"Nonnus, who wrote in the fifth century, reads trith, the third. As in ancient times all the numbers were written in the manuscripts not at large but in numeral letters, it was easy for g three, to be mistaken for v six. The Codex Bezae has generally numeral letters instead of words. Bengel observes that he has found the letter g gamma, THREE, exceedingly like the v episemon, SIX, in some MSS. Episemon = greek 'st' combined, similar appearance to final form sigma with a nearly flat top. Similar appearance to upper case gamma. The major part of the best critics think that trith, the third, is the genuine reading."
It is therefore clear that the reading in John is disputed, with one reading making sense chronologically, and the other not.
Fortunately, the manuscript evidence for the Bible is beyond compare in the ancient world, and comfortably informs us that we can be confident that the substance of the message presented in our modern English translations is the same as the substance of the message presented by the original authors themselves.