Holi and Holikā Dahana — pradoṣa, and the bhadrā exclusion
The popular claimThe fire has a rule, and the rule has an exception that swallows most years.
Of all the festival rules on this site, Holikā Dahana's is the one with the most machinery, because its main clause is nearly always overridden by its exception.
The main rule
The bonfire is lit on Phālguna pūrṇimā in the pradoṣa, the two and a quarter hours after sunset. That is the whole of the main clause.
The exception
A tithi is divided into two karaṇas, and the karaṇa named Viṣṭi, commonly called bhadrā, is held to be unfit for auspicious beginnings — a fire among them. Bhadrā recurs eight times a lunar month on a fixed pattern, and one of those times is the first half of pūrṇimā. So whenever pūrṇimā begins on the day of the pradoṣa, the pradoṣa is in bhadrā, and the main clause is blocked.
The nibandhas then give the fallbacks, in order. First: if bhadrā ends before midnight, light the fire after bhadrā ends. Second: if bhadrā runs past midnight, the fire may be lit in the bhadrā-puccha, the tail of the bhadrā — a short span in its final part that the texts treat as safe. Third: if none of that is workable, light it in the pradoṣa regardless, because pūrṇimā's evening is the day and the day cannot be moved. The Dharmasindhu lays these out in that sequence.
2027, computed
Pūrṇimā begins at 6:22 PM on Sunday 21 March and ends at 4:13 PM on Monday 22 March — Delhi, this site's engine. Sunday's sunset is 6:31 PM, so the pradoṣa runs to about 8:55 PM and pūrṇimā covers it. Monday's pradoṣa is after pūrṇimā has ended. So the day is Sunday 21 March — and the exception applies, because pūrṇimā began that afternoon.
The tithi lasts twenty-one hours fifty-one minutes, so bhadrā, its first half, runs from 6:22 PM on the 21st to about 5:17 AM on the 22nd — through the whole pradoṣa and well past midnight. The first fallback is closed. The second is the bhadrā-puccha: taken as the last three ghaṭīs, roughly 72 minutes, that is about 4:05 to 5:17 AM on the 22nd. That is the window the nibandha rule produces for 2027. Some traditions, holding to the third fallback, will light at the pradoṣa on the 21st and accept the bhadrā; the texts permit it and this page records both.
Holi — the colour, Dhuleṇḍī — follows on the day after the fire: Monday 22 March 2027.
What the fire remembers
The Bhāgavata Purāṇa, seventh book, tells of Prahlāda, whose devotion his father Hiraṇyakaśipu could not break. The episode of Holikā — the father's sister, who sat in the fire with the boy in her lap trusting a boon that fire would not touch her, and was taken by it while he was not — is in the Bhaviṣya and Narasiṁha Purāṇas rather than the Bhāgavata, and it is worth knowing which text carries which half. The bonfire is that fire, re-lit. The colours of the next morning belong to a different strand — the Vraja tradition of Kṛṣṇa and the gopīs — and the two have long since merged into one two-day festival.
Why the times above are not the times for you
Bhadrā is a fixed fraction of the tithi, so its span converts by the time difference; the pradoṣa and the puccha are measured from your own clock. A city ten hours behind Delhi may find the bhadrā ending before its midnight and the first fallback open. This site's panchang computes the karaṇa for the city you type.
What this page does not say
It does not say that a fire lit in bhadrā brings harm, and it does not tell you which fallback to follow. The texts give an order of preference; the reader's tradition decides which rung it stands on. The story of Prahlāda is a story about a devotion that did not need the fire to behave. This page does not add to it.
Source — Dharmasindhu and Nirnayasindhu on pradosha-vyapini purnima for Holika-dahana, on the bhadra (Vishti karana) prohibition, and on the fallback order; the Bhagavata Purana (book 7) for Prahlada, and the Bhavishya Purana (Uttara-parvan) and Narasimha Purana for the Holika fire; tithi, karana, sunrise and sunset computed by this site's panchang engine for Delhi
Every claim on this site names its source, and every calculator shows its arithmetic.