 The molad emtza'i (מולד אמצעי, average "molad", used for the traditional Hebrew calendar) is 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+1/3 seconds (or, equivalently, 29 days 12 hours and 44+1/18 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.