Dhanteras ot the first day of Divali, the Hindu festival celebrated on the trayodashi or thirteenth lunar day of Krishna Paksha (waning fortnight) in the Vikram Samvat Hindu calendar month of Karthik. Thus it is also known as Dhanvantri Trayodashi.
Dhanvantari, who is also worshipped on the occasion of Dhanteras, is considered the God of Ayurveda who imparted the wisdom of Ayurveda for the betterment of mankind, and to help rid it of the suffering of disease
Lord Dhanvantari, according to Hindu Mythology, emerged during Samudra Manthan, holding a Kalasha full of Amrit (an Ayurvedic herbal mix) in one hand and the sacred text about Ayurveda in the other hand. He is considered to be the Vaidya of Gods.