"Jesus was about thirty"
GradeWeak
Luke records that "Jesus himself began to be about thirty years of age" () at the start of his ministry. With a birth before the death of Herod the Great, as Matthew places it, usually dated to 4 BCE, Jesus' age fits a ministry beginning around 28/29 CE or a little later. The detail is consistent with both of the candidate dates for the crucifixion.
Weak. "About thirty" fits either year, so it does not help to choose between them.
Explore the counterarguments
It is a round number, an approximation, and cannot carry much weight in a precise chronology. It also depends on the date of Jesus' birth, which is itself known only approximately.