Hebrew calendar (astronomically called a lunar conjunction and, in Hebrew, a molad) is the moment at which the sun and moon are aligned horizontally with respect to a north-south line (technically, they have the same ecliptical longitude). The period between two new moons is a synodic month. The actual length of a synodic month varies from about 29 days 6 hours and 30 minutes (29.27 days) to about 29 days and 20 hours (29.83 days), a variation range of about 13 hours and 30 minutes. Accordingly, for convenience, a long-term average length, identical to the mean synodic month of ancient times (also
Lunar day daylight at a given point on the Moon would last approximately two weeks from beginning to end, followed by approximately two weeks of night. In some lunar calendars, such as the Hindu calendar, a lunar day, or "tithi", is defined as 1/30th of a lunar month, or the time it takes for the longitudinal angle between the Moon and the Sun to increase by 12 degrees. By this definition, lunar days generally vary in duration. Lunar day A lunar day is the period of time for Earth's Moon to complete one rotation on its axis with respect to the Sun.