2020
Tuesday, 29 December 2020
In 2020 the tithi runs from 7:54 am on 29 Dec to 8:58 am on 30 Dec; it is running at pradosh, the twilight just after sunset on Tuesday, 29 December 2020, so that is the day of Dattatreya Jayanti.
2021
Saturday, 18 December 2021
In 2021 the tithi runs from 7:24 am on 18 Dec to 10:05 am on 19 Dec; it is running at pradosh, the twilight just after sunset on Saturday, 18 December 2021, so that is the day of Dattatreya Jayanti.
Margashirsha Purnima, Wednesday, 30 December 2020. Purnima is running at sunrise: the day for the Purnima vrat and for bathing and gifts (snana-dana). Dattatreya Jayanti (29 Dec) is the same full moon, kept at dusk.
How the date is fixed
Dattatreya Jayanti falls on the full-moon day (Purnima) of the lunar month Margashirsha. The date is the day on which that tithi is running at pradosh, the twilight just after sunset.
About
Dattatreya Jayanti falls on the full moon of Margashirsha, in December. The birth is placed at pradosh, so the day whose evening carries Purnima is chosen, and the birth ceremony is performed in that window. Dattatreya, the combined form of Brahma, Vishnu and Shiva born to Atri and Anasuya, is the central figure of the Datta tradition of Maharashtra and the Deccan. Gangapur, Narsobawadi and Audumbar hold their main gatherings on this day, and the Gurucharitra is read in the week before.
How it is observed
The birth ceremony at dusk, Gurucharitra reading in the preceding week, and bhajan at Datta shrines.