“The common assertion seems reasonable that if Jesus "began his ministry" when he "was about thirty years of age" (Luke 3:23) and engaged in a three-year ministry ... then he was 33 years old at the time of his death. However, virtually no scholar believes Jesus was actually 33 when he died. Jesus was born before Herod the Great issued the decree to execute "all the male children in Bethlehem and in all that region who were two years old or under" (Matt. 2:16, ESV) and before Herod died in the spring of 4 B.C. If Jesus was born in the fall of 5 or 6 B.C., and if we remember that we don't count the "0" between B.C. and A.D., then Jesus would have been 37 or 38 years old when he died in the spring of A.D. 33 (as we believe is most likely). Even if Jesus died in the year A.D. 30 (the only serious alternative date), he would have been 34 or 35, not 33 years old.”
As the Christianity Today article points out, no major doctrine is affected by this common misconception, but it is something that is better to understand in speaking of Jesus’ life and in telling the story to others. You can read the CT article here.