We know that as the Lamb of God who corresponded to the original Passover lamb, Jesus died in the Jewish month of Nisan on the 14th day.
For the 10 years of the governorship of Pontius Pilate, under whom Jesus died, there is only a single year per the rules of the Jewish calendar, in which Nisan 14 fell on a Friday – 33 AD, so this is the year Jesus died.
The Jewish Passover is determined by the lunar cycle. There was a partial lunar eclipse on Friday, April 1, AD 33 (Gregorian calendar) or April 3, AD 33 (Julian calendar) or Nisan 14, 3793 (Hebrew calendar), the date of Jesus’ crucifixion.
We know Jesus was about 30 years of age when he was baptized, per Luke 3:23: “Now Jesus himself was about thirty years old when he began his ministry.” According to Jewish tradition and law, he would not have been able to teach in the synagogue until attaining the age of 30 (Numbers 4:3).
Four scriptures in John (2:13; 5:1; 6:4 and 12:1) suggest that Jesus made four distinct pilgrimages to Jerusalem for observance of the Passover during his ministry and was crucified during the fourth commemoration.
This supports the thought that his ministry was at least three years and can be further collaborated by the prophecy in Daniel 9:25-27 of Christ, the anointed one, being “cut-off” in the midst of the seventieth week of Israel’s favor.
This puts his birth in the year 2 BC. (That is the proper date and has been discussed with good evidence for more than a century. However, another popular date put Jesus’ birth at 4 BC because it was thought that the Herod who decreed the death of the innocents had died in 4 BC. However, we now know that the actual time of Herod’s death was in the early months of 1 BC, thus removing the objection to Jesus’ birth in 2 BC.)
Thus, if Jesus was born around October of 2 BC and baptized around October of 29 AD, then 2 + 29 – 1 = 30 years of age at his baptism. (When calculating across the BC/AD divide, the answer needs to be adjusted by 1 to account for the absence of a year “zero.”) Four years later in October of 33AD, he would be 34 years of age. But as he died 1/2 a year before October of 33AD, in the spring of that year, he would have been 33 1/2 years old. By our counting he would be said to be 33.