Unlike the solar calendar that guides Christian worship and the lunar calendar that governs Muslim religious observances, the Jewish year (from which both Christian and Muslim religious calendars stem) harmonizes solar and lunar rhythms. In this system, the lunar calendar has a certain primacy. In ancient times, special watch was kept in Jerusalem for the first appearance of the new moon, for this marked Rosh Hodesh, the beginning of a new month. This was honored everywhere
Volume 1, Page 32