Welcome to the page of Sidereal month calendar! All lunar calendars based on synodic months of 29.53059 days long. There is no calendar showing tropical or sidereal months. Tropical Month span = 27.321582 days (27 d 7 h 43 min 4.7 s). Sidereal month span = 27.321661 days (27 d 7 h 43 min 11.6 s). The calendar is prepared with 27 days Alpha months and 28 days beta months. Cycle 1: 2 alpha months and one beta month gives the average month span of 27.33333333 days. Cycle 2: 27th month is alpha and 28th month is beta. I.e., 28 months 9 beta months and 21 alpha months. Gives the length of 27.32142857 days gives some accurate closer to Tropical Month and sidereal month. Tropical month error 1 day in 6517.689 months. Sidereal month error 1 day in 4302.39 months Plan: Dates are named from 27 stars. Months are also named from 28 stars (Abhijit is the 28th star). Year is not aligned with this cycle.