I go by the black moon for the new moon because the month starts with the conjunction. What do you say?
In the scriptural calendar, the conjunction does not begin the month. At the conjunction no moon is visible. Deuteronomy 16:1 in the Hebrew tells us to “watch narrowly for the month (new moon) of green ears [of grain]” (RSB note). How can you watch closely for a new moon that cannot be seen? Often two or even three days of a dark moon precede the appearance of the crescent. Which invisible moon do you declare is the “right new moon”? Yahweh makes finding the first day of the month simple – it falls on the night you first sight a thin lunar crescent. No calculations necessary.
