Vasudeva Dwadashi is the festival ascribed to Lord Sri Krishna.
Lord Sri Krishna was originally born to Sri Vasudeva and Sri Devaki at Mathura as their eighth child. The Avatar as Sri Krishna was ordained by Sri Maha Vishnu to destroy Kamsasur and other demons. But the asura extinguishment was meant for the later time. So, it was arranged to shift Sri Krishna from Mathura to Gokulam.
Vasudeva Dwadashi occurs on the day next to Devshayani Ekadashi. It falls on the Ashada Shukla Paksha Dwadashi. For the Year 2021, it happens on Wednesday, 21st July 2021. The exact duration of the Dwadashi Tithi has to be ascertained from the respective regional calendars.
Vasudeva Dwadashi also marks the commencement of chathurmasa, the cluster of four months with lots of Vrats and functions. The day is also dedicated for worshipping Sri Mahalakshmi. The festival is also called as Sri Krishna Dwadashi.
As per Varaha Puran, it is believed that Sage Narada had told Vasudeva and Devaki to observe the Vrat on the Ashada Shukla Paksha Dwadashi to beget Sri Vishnu as their Son. Hence this Vrat is significant in the incarnation of Sri Krishna.
People wake up early in the morning. They place the idol / picture of Sri Krishna and Sri Mahalakshmi at the Puja place. Chandan, Kumkum and turmeric are placed on the Deities. The Puja place is decked up with flowers. Lamps and incense sticks are lit.
Slokam / Stotram invoking the Gods are recited. Puja and archana are done to the Deities. Fruits / Sattvic food are offered as Neivedyam. At the end of the Puja, aathi / Deepa aaradhana is done. The prasad is distributed.
Some devotees observe fasting for the day. Some devotees may observe partial fasting. Even if food is taken, only Sattvic food is consumed.
The devotees visit Sri Krishna / Sri Perumal temples. They have darshan and do archana. At temples, reading of Srimad Bhagavatham is done for the benefit of the devotees.
The devotees also feed the cows and their calves with jaggery, chappathi and green grass. Feeding of cows and making donation to the needy and the poor are considered auspicious on this day.
Chanting of Sri Vishnu Sahasra Nama and Mahalakshmi Slokams is considered auspicious.
It is believed that observing of Vasudeva Dwadashi shall result in more prosperity and attainment of moksha.