Was there a co-regency of Tiberius and Augustus?

Question

Caesar Augustus was the first Emperor of the Roman Empire. He succeeded the dictator Julius Caesar and was succeeded by Caesar Tiberius. Some claim Tiberius was co-regent with Augustus for a couple years prior to Augustus' death, but this is disputed. A co-regency is the situation where a monarchical position (such as king, queen, emperor or empress), normally held by only a single person, is held by two or more.

This is an important issue to historians, as it affects the dating of the life of Jesus. Had there been a co-regency, Jesus could have started His ministry as early as AD 26 or 27, allowing for AD 30 to be the date of Jesus' death. Had there been no co-regency, His ministry would have started at about AD 29, putting His death around AD 33.

An article from the creationist web site Answers In Genesis says (see Conclusion)

[S]ome have postulated a co-regency (joint rule) of Tiberius and Augustus during the last few years of Augustus’s reign. However, there is no reliable ancient historical evidence for such co-regency.

[emphasis mine]

Is there any historical evidence for Caesar Tiberius having a co-regency with his predecessor Caesar Augustus?

Answer 1

The author of the Answers in Genesis article is likely incorrect.

Tiberius officially was solely Roman emperor in A.D. 14. However, to quote Garret G. Fagan, a history professor at Penn State:

From A.D. 4 to 14 Tiberius was clearly Augustus's successor. When he was adopted, he also received grants of proconsular power and tribunician power; and in A.D. 13 his proconsular power was made co-extensive with that of Augustus .[[11]] In effect, Tiberius was now co-princeps with Augustus so that when the latter finally died on 19 August A.D. 14, Tiberius's position was unassailable and the continuation of the Principate a foregone conclusion.

Source

Evidence for this appears to be the ancient Roman historian Suetonius. To quote wikipedia's article on Tiberius:

However, according to Suetonius, after a two-year stint in Germania, which lasted from 10−12 AD, "Tiberius' returned and celebrated the triumph which he had postponed, accompanied also by his generals, for whom he had obtained the triumphal regalia. And before turning to enter the Capitol, he dismounted from his chariot and fell at the knees of his father, who was presiding over the ceremonies.” "Since the consuls caused a law to be passed soon after this that he should govern the provinces jointly with Augustus and hold the census with him, he set out for Illyricum on the conclusion of the lustral ceremonies."

Thus according to Suetonius, these ceremonies and the declaration of his "co-princeps" took place in the year 12 AD, after Tiberius return from Germania.

A link to the relevant translation of Suetonius which supplies the quotes in the above.

Suetonius appears to be reliable, and the author from Answers in Genesis has provided no reason to doubt his account.

Note that Princeps civitatis ("First Citizen") is the official title of the Roman Emperor.

Answer 2

Christ was born at least by 4 BC for that is when King Herod died. And we know He started His ministry at age 30 according to Luke 3:23, which was His baptism signifying His anointing for ministry. So, if born 4 BC, He was 30 in AD 27. He was crucified in 31 AD at age 33. So, Tiberius was co-regent in 12 AD and his 15th year would be 27 AD. And if my understanding is correct we must acknowledge that 14 AD was the year he became ruler, yet, his succession year is never counted as a year. So, the 15th year of Tiberius was 27 AD and not 29 AD if we date everything from the perspective of co-regent in Ad 12. And Daniel 9: 25 further supports 27 Ad for His baptism, for it says 69 weeks would transpire from the going forth of the commandment to restore and build Jerusalem until the Messiah the Prince. So, if you use the year 457 BC for the decree by Artaxerxes, and go forward 69 weeks - of years, (69x7=483 years) you come to AD 27. Some use 458 BC but it all depends on what calendar you use, the Jews used - fall to fall, so 457 is correct. On page 643 in the works of Josephus, Josephus says that Christ was 30 when he was baptized, so if born 4 BC the year would have to be 27 AD.