During the early part of the Kulasekara period, the southern region from Nagercoil to Thiruvalla was ruled by Ay kings, who lost their power in the 10th century, making the region a part of the Kulasekara empire.[84][85] Under Kulasekhara rule, Kerala witnessed a developing period of art, literature, trade and the Bhakti movement of Hinduism.[86] A Keralite identity, distinct from the Tamils, became linguistically separate during this period around the seventh century.[87] The origin of Malayalam calendar dates back to year 825 CE.[88][89][90] For local administration, the empire was divided into provinces under the rule of Naduvazhis, with each province comprising a number of Desams under the control of chieftains, called as Desavazhis.[86] Mamankam festival, which was the largest native festival, was held at Tirunavaya near Kuttippuram, on the bank of river Bharathappuzha.[9][60] Athavanad, the headquarters of Azhvanchery Thamprakkal, who were also considered as the supreme religious chief of the Nambudiri Brahmins of Kerala, is also located near Tirunavaya.[91][60]