Upvote:3
Reading the Wikipedia article cited in the question a little further we come to the Chronology section. In this we read that most scholars consider the most likely date for the Crucifixion to be April in the year 30 AD.
If Jesus was born in the Autumn of 5 BC, for example, He would have turned 4 in the year 1 BC, and turned 5 in the year 1 AD. (There was no Year Zero.) Having turned 5 in the year 1 AD He would turn 25 in the year 21 AD and would have celebrated His thirtieth birthday (if indeed He celebrated birthdays) in Autumn of the year 26.
If He began His ministry in Autumn 26, very close to His 30th birthday, then three years later He would have turned 33 in Autumn 29, and still been 33 at the time of the Crucifixion, and Resurrection, in the Year 30 AD.
On this basis His ministry would have begun in the 15th year since Tiberius became co-emperor.
We do not know for sure any of the dates, but there is no inconsistency in the assumptions made.