In the fifteenth year of the reign of Tiberius Caesar: Tiberius Caesar began to rule with his stepfather, Caesar Augustus, in AD 11. He became the sole emperor in AD 14 and ruled until AD 37. Luke may be counting from either AD 11 or AD 14. If so, John began his public ministry around AD 26/27 or AD 29/30. Jesus began his own ministry soon after John.
Pontius Pilate was governor of Judea from AD 26 to 36 (see “Pontius Pilate” Profile).
Herod tetrarch of Galilee: See “Herod Antipas” Profile.
Antipas’s half-brother Philip was another son of Herod the Great. Philip ruled as tetrarch of the region northeast of Galilee from 4 BC until his death in AD 34. Tetrarch means “the ruler of a fourth of a kingdom.” The term later meant any minor ruler. Philip was a half brother of both Antipas and Herod Philip (Matthew 14:3; Mark 6:17).