The Tamil calendar is a sidereal Hindu calendar used in Tamil Nadu, India. It is also used in Puducherry, and by the Tamil population in Malaysia, Singapore, Mauritius and Sri Lanka. It is also used by Telugu speaking people in Tamil Nadu. It is used today for cultural, religious and agricultural events, with the Gregorian calendar largely used for official purposes both within and outside India. The Tamil calendar is based on the classical Hindu solar calendar also used in Assam, West Bengal, Kerala, Manipur, Nepal, Odisha, Rajasthan and Punjab.
There are several festivals based on the Tamil Hindu calendar. The Tamil New Year follows the nirayanam vernal equinox and generally falls on 14 April of the Gregorian year. 14 April marks the first day of the traditional Tamil calendar and this remains a public holiday in both Tamil Nadu and Sri Lanka.