New Moon
The accurate determination of the new Moon was always of the utmost importance to the Hebrews, because if they were not precise with the exact time of the new moon it would upset their whole calendar, and the Lord of the calendar would be sought on the wrong days. If the Lord is indeed the Lord of times and seasons and designed a calendar, then it was their duty to observe it with accuracy and heart-felt passion.
During the time of Herod�s Temple the high priest was the one chosen to announce the New Moon from the Temple, based upon the testimony of two trustworthy witnesses. Once the announcement was made torches were lit on the Mount of Olives, which was a signal to those waiting upon other hills, even distant hills, that the New Moon had appeared over Jerusalem and to celebrate the New Moon with those even of the dispersion.
The Jewish Calendar in Ancient Hebrew History