Narasimha Jayanti marks the day on which Vishnu is said to have appeared as Narasimha, half man and half lion, to protect his devotee Prahlada. It falls in the bright fortnight of Vaishakha, on Chaturdashi, the fourteenth tithi, the day before the full Moon of Buddha Purnima. It is observed by Vaishnavas, especially in Andhra Pradesh, Telangana, Karnataka and Tamil Nadu, where Narasimha has famous temples such as Ahobilam, Simhachalam and Yadagirigutta.
Month and tithi
The festival is the Shukla Chaturdashi of Vaishakha, explained on the Chaturdashi page. The month is the same in the amanta and purnimanta calendars for the bright fortnight.
The story
The Bhagavata Purana and the Vishnu Purana tell of Hiranyakashipu, an asura king who had received a boon that he could be killed neither by man nor beast, neither indoors nor outdoors, neither by day nor by night, and neither on the ground nor in the sky, nor by any weapon. Drunk with power, he demanded that all worship him alone. His young son Prahlada, a devotee of Vishnu, refused. After many attempts to harm the boy had failed, Hiranyakashipu asked mockingly whether Vishnu was in the pillar before him. As he struck the pillar, Vishnu emerged as Narasimha. At dusk, on the threshold of the hall, with the king laid across his lap and claws for weapons, the form met every condition of the boon, and the tyrant was destroyed. The story is read as a story of devotion and of protection for the faithful, and each of its tellings has its own details.
How the vrat is kept
Devotees fast through the day, bathe, and keep an image of Narasimha or Vishnu with Lakshmi. A sankalp, a resolve to keep the vrat, is taken around midday, and the main puja is held in the evening, at dusk. It includes panakam (jaggery water), vadapappu (soaked moong dal), fruit and tulsi leaves, and verses such as the Narasimha Kavacham and the Lakshmi Narasimha Karavalamba Stotram. In some homes a night vigil follows.
How the day and the parana are fixed
The rule used here follows Drik Panchang: the festival is on the civil day on which Chaturdashi is in force at sunset; if it is so on two days, the second is taken. The table gives the Sayahna puja window, from the last fifth of the day until sunset, and the sankalp window in the middle of the day is in the data too.
The fast is broken the next day. If Chaturdashi is over by sunrise, the parana is after sunrise; if it runs on past sunrise but ends within three-quarters of the day, it is after the tithi ends; and if it runs on beyond that, the fast is broken before the middle of the day. If your family follows a stricter Vaishnava rule, which can name a different day, follow it.
Why cities differ
The tithi starts and ends at one instant, but sunset is at a different clock time in every city. A Chaturdashi that ends shortly before sunset in one city may still be in force at sunset in another, so the day moves. The table shows each city, and for places not in it the any-city tool works out the same.
A calm note
A fast is a personal choice. If you are unwell, pregnant, elderly or on medicine, a lighter fast is accepted, and a doctor is the right person to ask. The day is about steady devotion and not about hunger.