2019
Friday, 25 October 2019
In 2019 the tithi runs from 7:08 pm on 25 Oct to 3:46 pm on 26 Oct, and it never reaches pradosh, the twilight just after sunset, so the day on which it begins is taken: Friday, 25 October 2019.
2020
Friday, 13 November 2020
In 2020 the tithi runs from 9:30 pm on 12 Nov to 5:59 pm on 13 Nov; it is running at pradosh, the twilight just after sunset on Friday, 13 November 2020, so that is the day of Dhanteras.
How the date is fixed
Dhanteras falls on the thirteenth day of the dark half of the lunar month Ashwina (Krishna Trayodashi). The date is the day on which that tithi is running at pradosh, the twilight just after sunset. In the North Indian (purnimanta) calendar the same fortnight is counted in Kartika.
About
Dhanteras falls on the thirteenth tithi of the dark half of Ashwina in amanta reckoning (Kartika Krishna Trayodashi in the north), two days before Diwali, in October or November. The governing period is pradosh, the hour and a half after sunset, so the day whose dusk carries Trayodashi is chosen. The day is also Dhanvantari Jayanti, the birth of the physician of the gods, and the evening of the Yama deepa, a lamp placed outside the door. Buying metal utensils on this day is the familiar custom.
How it is observed
Lakshmi and Dhanvantari worship at pradosh, a lamp for Yama outside the door, and the purchase of utensils or metal.