Scholars have pretty well agreed that Herod the Great died in the year 4 B.C. By this we know that the events of Jesus’ birth, the visit of the wise men, the family’s flight into Egypt, and the slaughter of the boys in Bethlehem all had to have occurred prior to this time.
According to Josephus there was an eclipse of the moon shortly before Herod’s death (Antiquities of the Jews, 17.6.4), and astronomers tell us that just such an eclipse took place on March 13th of that year. Is this the eclipse Josephus was talking about? Probably so. Josephus also makes clear that Herod died before Passover, which was about 29 days after said eclipse.
If you take the lunar eclipse of March 13 to be the same eclipse Josephus referred to in connection with the time of Herod’s death, as I do at this point, then you have narrowed the window for this significant landmark date to about a 29-day period. Not bad at all, if you ask me.
So for now, let’s say that Herod died sometime in late March or early April of the year 4 B.C.