The full moon holds enormous importance in the Hindu calendar. Referred to as Purnima that is when the Moon appears in its complete form, it is hailed as an auspicious day for observing a fast and worshipping the Ishta Devta. This particular occasion is also observed as Dattatreya Jayanti. In Hinduism, Lord Dattatreya is an avatar of the Trimurti, i.e., Lord Brahma, Lord Vishnu, and Lord Mahesh.
The Purnima of the Margashirsha month is doubly auspicious because the month itself is believed to be the most sacred.
On Purnima Tithi, devotees observe a day-long fast from sunrise to moonrise and worship the Sun and Moon gods by offering salutations with water. This month usually comes in Gregorian December, but the Full Moon date keeps changing every year.
The Margashirsha Purnima Vrat will be observed on December 18, 2021.
Purnima Tithi will begin - 7:24 am, December 18
Purnima Tithi will end - 10:05 am, December 19
Margashirsha Purnima is said to be the day when Bhagwan Dattatreya came into being. The God who has three faces is believed to have the combined powers of Lord Shiva, Lord Vishnu and Lord Brahma. It was also when the Annapurna form of Mother Goddess Parvati took birth on this day. She is hailed as the Goddess of food. Devotees also observe Annapurna Jayanti on Margashirsha Purnima Tithi.
On Purnima Tithi, devotees take a bath in the holy waters of rivers such as the Ganga, the Yamuna, the Narmada etc. This Purnima Tithi is also known as Battisi Purnima. On this day, the good deeds yield results equal to charity done 32 times. Hence, the name Battisi. Belief also suggests that by observing a vrat on this day, people can fulfil their wishes.