synodic month

1. There are two kinds of almanac both in Historical Record Almanac and Record Of Han Almanac which have the same start-point but the synodic month and the average of period different.
   《史记·历书》和《汉书·律历志》分别记载了具有同一起算点，但朔望月与回归年平均值不同的两种历。
2. Selection of the Constant of Synodic Month in Ancient Chinese Calendars
   中国古代历法中之朔望月常数的选择

noun

1. the period between successive new moons (29.531 days)

   Synonym:    lunar monthmoonlunation