The Tamil calendar is a sidereal solar calendar used by the Tamil people of the Indian subcontinent. It is also used in Puducherry, and by the Tamil population in Sri Lanka, Malaysia, Singapore, and Mauritius. It is used in contemporary times 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. Description The calendar follows a 60-year cycle that is also very ancient and is observed by most traditional calendars of India and China. This is related to 5 12-year revolutions of Jupiter around the Sun and one that adds up to 60 years and the orbit of Nakshatras (stars) as described in the Surya Siddhanta. In the Gregorian year , the Tamil year starts on 14 April , Kaliyuga . The Vikrama and Shalivahana (Saka) eras are also used. There are several references in early Tamil literature to the new year. Nakkeerar, Sangam period author of the Neṭunalvāṭai, wrote in the third century CE that the Sun travels each year from Mesha/Chittirai in mid-April through 11 successive signs of the zodiac. Kūdalūr Kiḻar in the third century CE refers to Mesha Rāsi/Chittirai i.e. mid-April as the commencement of the year in the Puṟanāṉūṟu. The Tolkappiyam is the oldest surviving Tamil grammar text that divides the year into six seasons where Chihthirrai i.e. mid-April marks the start of the Ilavenil season or Summer. The 5th century Silappadhigaaram mentions the 12 rāsigal or zodiac signs that correspond to the Tamil months starting with Mesha/Chittirai in mid-April. The Manimekalai alludes to this very same Hindu solar calendar as we know it today Adiyarkunalaar, an early medieval commentator or Urai-asiriyar mentions the twelve months of the Tamil calendar with particular reference to Chittirai i.e. mid-April. There were subsequent inscriptional references in Pagan, Burma dated to the 11th century CE and in Sukhothai, Thailand dated to the 14th century CE to South Indian, often Vaishnavite, courtiers who were tasked with defining the traditional calendar that began in mid-April. 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 is a public holiday in the state of Tamil Nadu, Sri