Tiberius & Philip
About this time it was that Philip, Herod's ' brother, departed this life, in the twentieth year* of the reign of Tiberius, after he had been tetrarch of Trachonitis and Gaulanitis, and of the nation of the Bataneans also, thirty-
Josephus, Antiquities 18.106.
*= Manuscripts from 1544AD or older all have twenty-
Philip died in the 22nd year of Tiberius after ruling for 37 years.
Philip started his reign shortly after Herod died. So if Philip started in 1BC then Herod must have died shortly before that.
The widely accepted date for Herod’s death was 4BC for a long time. But even Wikipedia starts to catch up because the list 37– c. 4 BCE/ 1 CE -
That allows for Jesus to be born as late as 1 BC.
Conclusion #1: Philip started his reign on 1 BC.
Conclusion #2: Herod died in or shortly before 1 BC.
Conclusion #3: Jesus was born in 1 BC or earlier.