Tamil Calendar, a differential form of the old Hindu calendar, is based on the sidereal year system. It starts in the middle of April and has twelve months with a varying number of days. A maximum of 32 days are possible in a month. Same as any other calendar, the Tamil calendar also has a seven-day week. Based on the five Jovian periods, each year in the calendar takes a different name and follows a 60-year cycle. The 12 months (in the order of January to December) are Thai, Maasi, Panguni, Chithirai, Vaikasi, Aani,
, Aavani, Purattasi, Aippasi, Karthikai and Markazhi. The Tamil New Year falls in the month of Chithirai.