Vishnu and Shiva worshipped together; Harishchandra Ghat aarti in Varanasi

Vaikuntha Chaturdashi, on Kartika Shukla Chaturdashi, is the rare day when Lord Vishnu and Lord Shiva are worshipped together as one (Hari-Hara). The Shiva Purana relates that Vishnu came to Kashi to worship Shiva with a thousand lotuses. Shiva, to test him, hid one lotus; finding one short, Vishnu, called 'Kamalanayana' (lotus-eyed), offered one of his own eyes in its place. Moved, Shiva restored his eye and gave him the Sudarshan Chakra. Shiva also declared that whoever worships Vishnu on this day will attain Vaikuntha, Vishnu's abode — hence the name. It is the only day on which tulsi is offered to Shiva and bilva to Vishnu, and in Kashi Vishwanath, Vishnu is installed in the sanctum and each is worshipped as if worshipping the other. Vishnu is worshipped at midnight (Nishita Kaal) with a thousand lotuses and the Vishnu Sahasranama; Shiva is worshipped at dawn (Arunodaya) the next morning. In Ujjain, Mahakaleshwar is carried in a grand procession to the Gopal Mandir for 'Hari-Har Milan', where Shiva hands over the charge of the universe to the newly awakened Vishnu, exchanging garlands of bilva and tulsi. In Rishikesh and Gaya, lamps are floated on the river.

Fast through the day and night; break after the dawn Shiva puja.