Tiberius Caesar

Luke 3:1, ". . . Now in the fifteenth year of the reign of Tiberius Caesar, . . ."

What do you understand that in the 15th year of his reign to have been?
His reign began in September of 14 A.D.

 

If we understand the when Tiberius Caesar's reign starts at year one, not at zero. Then between September 14 A.D. to September 15 A.D. can be understood to be in the second year for Luke's in the 15th year to be September 27 A.D. through September 28 A.D.

In John's gospel account he explicitly mentions three feasts to be Passovers. Which can be as understood to be in 28 A.D., 29 A.D. and 30 A.D..

 

Yes, this has been claimed. But I have never found its historical source. It was as if it really did not exist. Maybe you know were to find it. Sir Isaac Newton goes for the 29 A.D. So his 33 A.D. Friday Julian date April 3rd is commonly accepted. If one accepts Mark 14:12-16 - Mark 15:41 the 33 A.D. would place the crucifixion on the Sabbath which contradicts Mark 15:42. Mark 14,:12 - Mark 15:42 requires the 30 A.D. date. The whole reason I present the view I do. Calendar Converter

 

My primary source is my Adam Clarke Commentary [1810-1825]. Printed edition, here My Sword electronic edition:
"Verse 1. Fifteenth year] This was the fifteenth of his principality and thirteenth of his monarchy: for he was two years joint emperor, previously to the death of Augustus.

Tiberius Caesar] This emperor succeeded Augustus, in whose reign Christ was born. He began his reign August 19, A.D. 14, reigned twenty-three years, and died March 16, A.D. 37, aged seventy eight years. He was a most infamous character. During the latter part of his reign especially, he did all the mischief he possibly could; and that his tyranny might not end with his life, he chose Caius Caligula for his successor, merely on account of his bad qualities; and of whom he was accustomed to say, This young prince will be a SERPENT to the Roman people, and a PHAETHON to the rest of mankind."

 

Is there any historical evidence for a co-regency of Tiberius and Augustus?

 

The link seems to be there. But when I go to it, that info becomes missing.
Tiberius - Wikipedia

Suetonius - Wikipedia

 

". . .
Thus, when in AD 13, the powers held by Tiberius were made equal, rather than second, to Augustus' own powers, he was for all intents and purposes a "co-Princeps" with Augustus, and, in the event of the latter's passing, would simply continue to rule without an interregnum or possible upheaval.[37]
. . . ."

How many more months than 12 prior to September 14 A.D.? What month did the year begin?