Yama and Yamuna
Bhai Dooj falls on Kartik Shukla Dwitiya, the last of the five days of Diwali. Its best-known story is of Yama, the god of death, visiting his sister Yamuna on this day. She welcomed him with tilak and a meal, and he blessed every brother who visits his sister on Dwitiya with long life; the day is also called Yama Dwitiya.
It is Bhai Phonta in Bengal, Bhau Beej in Maharashtra, Goa and Karnataka, and Bhai Tika in Nepal, where the tika of seven colours is given on the last day of Tihar.
