Molad based on a constant interval cycle that is widely but incorrectly regarded as an approximation of the time in Jerusalem of the mean lunar conjunction. Each "molad" moment occurs exactly 29 days 12 hours 44 minutes and 3+/ seconds (or, equivalently, 29 days 12 hours and 44+/ minutes) after the previous "molad" moment. This interval is numerically exactly the same as the length of the mean synodic month that was published by Ptolemy in the Almagest, who cited Hipparchus as its source. Although in the era of Hipparchus (2nd century BC) this interval was equal to the average time between
Lunar month Lunar month In lunar calendars, a lunar month is the time between two successive syzygies (new moons or full moons). The use of the lunar month varies by which culture has utilized the method, the main difference being when the "new" month begins. This article deals with the definitions of a 'month' that are mainly of significance in astronomy. For other definitions, including a description of a month in the calendars of different cultures around the world, see: month. In Shona, Middle-Eastern, and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction