The First day is called DHANTERAS or DHANTRAYODASHI which falls on the thirteenth day of the dark fortnight in the month of Kartik (October-November), i.e. two days before Diwali. The word "Dhan" means wealth. God Yama is worshipped on this day to provide prosperity and well being. Legends:

According to legend, when the gods and demons churned the ocean for Amrut or nectar, Dhanavantri(the physician of the gods and an incarnation of Vishnu) emerged carrying a jar of the elixir. Both the Asuras and the Devas wanted the ambrosia, but finally Vishnu with a slight of hand managed to give the immortal nectar to the Gods and the Asuras where defeated. Thus the churning of the ocean resulted in the immortality of the Devas and was the reason for Lakshmi`s emergence. Another Legend : A very interesting story about this day is of the sixteen year old son of King Hima. As per his horoscope he was doomed to die by a snake-bite on the fourth day of his marriage. On that particular fourth day of his marriage his young wife did not allow him to sleep. She laid all the ornaments and lots of gold and silver coins in a big heap at the entrance of her husband`s boudoir and lighted innumerable lamps all over the place. And she went on telling stories and singing songs. When Yam, the god of Death arrived there in the guise of a Serpent his eyes got blinded by that dazzle of those brilliant lights and he could not enter the Prince`s chamber. So he climbed on top of the heap of the ornaments and coins and sat there whole night listening to the melodious songs. In the morning he quietly went away.
Thus the young wife saved her husband from the clutches of death. Since then this day of Dhanteras came to be known as the day of "YAMADEEPDAAN" and lamps are kept burning throughout the night in reverential adoration to Yam, the god of Death.