Based on astrological calculations contained in the book “Star of the Magi,” the actual date was April 17, 6 B.C.
The problem with that date is that April would be when an agricultural society, like most of Roman subjects would have been, starts planting their crops. After a long winter, their wealth would be at a low point and there would be very little to collect, which was the reason why Mary and Joseph were going to Bethlehem.