The Happy Dhanteras is one of the prominent festival that is celebrated in the Hindu culture during the days of Happy Diwali. With that being said, the festival of Dhanteras is actually the first day among the 5 days of Happy Diwali celebrations.
Dhanteras is celebrated on the 13th lunar day of Krishna Paksha (which is the dark fortnight) in the hindu calendar month of Kartik.
One of the myth in the festival of Happy Dhanteras is that lightning a lamp in the south direction can bring up the fortune, prosperity and wealth in the family. Also, there lies a historical belief and a story that when asked to the Yamraja (The God of Death) that what should be done to avoid the premature death? In the response, the Yamraja replied that the person should put a lamp in the southern direction of the Yamrajas name in their house.