The problem is that Jesus died in 33 CE on April 1, according to our modern calendar. Since we know that Jesus was approximately 33.5 years old at the time of his death, that gives us a means to calculate his year of birth.
We are clearly told that Jesus was about 30 when his ministry started:
Luke 3:
And, Jesus himself, was, when he began, about thirty years of age, being the son, as was supposed—of Joseph, of Heli: (Rotherham)
His ministry was according to Daniel, 3.5 years in length
Daniel 9:
27 And he will confirm a covenant to the many, for one week,—but, in the middle of the week, will cause sacrifice and present to cease, and, in his stead, [shall be] the horrid abomination that astoundeth, even till, a full end, and that a decreed one, shall be poured out on him that astoundeth.
One week is seven years, the middle of the week when Jesus was killed would then be 3.5 years.
One reference work says the following:
Quoting:
Summary of evidence. Summing up, then, since Jesus’ death took place in the spring month of Nisan, his ministry, which began three and a half years earlier according to Daniel 9:24-27, must have begun in the fall, about the month of Ethanim (September-October). John’s ministry (initiated in Tiberius’ 15th year), then, must have begun in the spring of the year 29 C.E. John’s birth therefore would be placed in the spring of the year 2 B.C.E., Jesus’ birth would come about six months later in the fall of 2 B.C.E., his ministry would start about 30 years later in the fall of 29 C.E., and his death would come in the year 33 C.E. (on Nisan 14 in the spring, as stated).
Also this paragraph, quoting:
On this basis, John’s birth occurred 30 years before he began his ministry in Tiberius’ 15th year, hence somewhere between the latter half of 3 B.C.E. and August or September of 2 B.C.E., with Jesus’ birth following about six months later.
If you have further questions or comments, I'll try to assist.