Computus week before the Gregorian Easter in 1724, 1744, 1778, 1798, etc. The Easter cycle groups days into lunar months, which are either 29 or 30 days long. There is an exception. The month ending in March normally has thirty days, but if 29 February of a leap year falls within it, it contains 31. As these groups are based on the lunar cycle, over the long term the average month in the lunar calendar is a very good approximation of the synodic month, which is days long. There are 12 synodic months in a lunar year, totaling either 354 or
Karkaṭa followed by the solar month of Siṃha. The Karkata month is called "Adi" in the Tamil Hindu calendar. The ancient and medieval era Sanskrit texts of India vary in their calculations about the duration of Karkata, just like they do with other months. For example, the "Surya Siddhanta" calculates the duration of Karkata to be 31 days, 11 hours, 24 minutes and 24 seconds. In contrast, the "Arya Siddhanta" calculates the duration of the Karkata month to be 31 days, 11 hours, 13 minutes and 36 seconds. The Indian solar month names are significant in epigraphical studies of South Asia.