Answer:
Actually, to avoid confusion, it might be better to call him "John the Baptizer." Even though "John the Baptist" is a correct term, it can confuse people who are familiar with those Christians who call them selves "Baptists". Christian Baptists go back in history to about 1609, long after John the Baptizer was gone.
John started his ministry before Jesus and ended his ministry before Jesus. Since John was a few months older than Jesus, that meant that he ended his ministry perhaps around the age of 33. Unfortunately, we don't know exactly when he started.