Pilate's Governorship may have begun sooner in AD 17 or 18.

Here is an article on the subject arguing it could be the case based mostly on Roman Coinage.

http://www.academia.edu/8296217/The_Chronology_and_Tenure_of_Pontius_Pilate_New_Evidence_for_Re-dating_the_Period_of_Office._Judaea_and_Rome_in_Coins_65_BCE_-_135_CE._The_Numismatic_Circular_pp._1-7._Kenneth_L%C3%B6nnqvist

The above Article is behind a Paywall now, I first read it years ago when it wasn't so my memory of exactly how it made it's argument is foggy. 

There is a potential argument for this model from Josephus I have noticed that I don't think that article included.  Which is notable because something Josephus said is also basically the sole reason for the more common AD 26 date.

In Antiquities of The Jews Book 18. the last thing Josephus talks about at the end of chapter 2 before introducing Pilate in chapter 3 is the Death of Antiochus III of Commagene who died in AD 17.  The first three sections of chapter 3 are stories about affairs when Pilate was Governor, one of them being the Crucifixion of Jesus.

Then section 4 begins a long account of calamities that befell the Jews and Egyptians in Rome.  Tacitus Annals II records those same events, his Annals are explicitly year by year and he places them in AD 19 (the Year of the Consulship of Silanus and Balbus), the same year as the death of Germanicus.

Now the above article stresses how this need not change assumptions about the chronology of The Gospels, they're expanding Pilate's administration not moving it, he was still governor during the Passovers of 27-36, with myself long favoring the Passion being in AD 30.

However I have been flirting with the possibility of moving it down.  It would make my arguments for sooner Nativity Dates (Like 12 BC) even more plausible.  The 12 BC Model would have Jesus turn 30 in 19 and his 30th Year begin in 18. 

Apparently Tertullian had said there were 52 years between the first Advent and the fall of Jerusalem to Titus.  Which points us to AD 18.

What about the 15th Year of Tiberius?  Well I've already said more then once that Jesus Baptism could have actually happened before that, it's simply when John was arrested that happened then, which I do view as possibly merely months or even weeks before the Passover of the Crucifixion.  And it could be Luke was using a source counting from when Tiberius truly became Augustus's Heir and given the Tribunician power in AD 4 which can give us a 15th Year that begins in 18 and ends in 19.

Slavonic Josephus seemingly has John The Baptist begin being active while Archelaus is still in power.  I'm highly skeptical of Slavonic Josephus but I did feel like noting that. 

This redating of the Crucifixion mess up the 70 Weeks Model I have argued for on this blog.  

Whether or not when the Crucifixion happened should be affected, I am convinced of these arguments for beginning Pilate's Governorship almost a decade sooner.