The religion of the ancient Tamils closely follow roots of nature worship and some elements of it can also be found in Tamil Shaiva Siddhanta traditions. In the ancient Sangam literature, Sivan was the supreme God, and Murugan was the one celebrated by the masses; both of them were sung as deified Tamil poets ascending the Koodal academy. The Tamil landscape was classified into five categories, "thinais", based on the mood, the season and the land. "Tolkappiyam", one of the oldest grammatical works in Tamil mentions that each of these "thinai" had an associated deity such as Kottravai (Mother goddess i.e. Kali) and Sevvael (Murugan) in Kurinji (the hills), Thirumal (Maayon) in Mullai (the forests), Vendhan (Wanji-ko or Seyyon i.e. Indra) in Marutham (the plains i.e. Vayu), and Kadaloan (Varuna) in the Neithal (the coasts and the seas). Other ancient works refer to Maayon (Maal) and Vaali. The most popular deity was Murugan, who has from a very early date been identified with Karthikeya, the son of Siva. Kannagi, the heroine of the "Silappatikaram", was worshiped as Pathini (பத்தினி) by many Tamilians, particularly in Sri Lanka. There were also many temples and devotees of Thirumal, Siva, Ganapathi, and the other common Hindu deities. The ancient Tamil calendar was based on the sidereal year similar to the ancient Hindu solar calendar, except that months were from solar calculations, and originally there was no 60-year cycle as seen in Sanskrit calendar. The year was made up of twelve months and every two months constituted a season. With the popularity of Mazhai vizhavu, traditionally commencement of Tamil year was clubbed on April 14, deviating from the astronomical date of "vadavazhi vizhavu". Musicians, stage artists, and performers entertained the kings, the nobility, the rich and the general population. Groups of performers included:   Together with the poets ("pulavar") and the academic scholars ("saandror"), these people of talent appeared to originate from all walks of life, irrespective of their native profession.