Dhanteras, also known as Dhanatrayodashi or Dhanvantari Trayodashi, is the first day that marks the festival of Diwali in India and the festival of Tihar in Nepal.
Dhanteras is celebrated on the thirteenth lunar day of Krishna Paksha (dark fortnight) in the Vikram Samvat Hindu calendar month of Karthik. Dhanvantari, who is also worshipped on the occasion of Dhanteras, is 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.