Molad is the Hebrew term for the calculated average lunar conjunction used in the traditional Jewish calendar.
In calendar calculation, a molad is not an observation of the moon’s visible crescent. It is a mathematically defined moment based on a fixed mean lunar month. The traditional molad interval is 29 days, 12 hours, 44 minutes, and 3⅓ seconds, expressed in the calendar’s historical unit of “parts.”
The molad of Tishrei is especially important because it helps determine the calendar date of Rosh Hashanah. Calendar rules can postpone the festival after the calculated molad, so the molad itself is not always the instant when Rosh Hashanah begins.
Readers sometimes confuse molad with the actual astronomical new moon. The fixed calendar’s molad is an average calculation, whereas the true conjunction varies because the Moon’s orbit is not perfectly uniform. The term therefore belongs to calendar arithmetic, not to a claim that observers see a new moon at that exact moment.