Rakṣā Bandhan — aparāhna, and the bhadrā exclusion
The popular claimThe afternoon rule and the bhadrā rule collide almost every year. 2027 is one of those years.
Rakṣā Bandhan has a clean rule and an exception that fires in most years, and the interaction between the two is why the "correct time to tie the rākhī" is argued over every August.
The main rule
Śrāvaṇa pūrṇimā, in the aparāhna — the fourth of the five equal parts of daylight, the two-hour window starting a little after one in the afternoon. That is where the rite belongs.
The exception
The first half of every pūrṇimā is the karaṇa Viṣṭi, called bhadrā, and the nibandhas exclude it for this rite in strong terms. Since pūrṇimā lasts about a day, its first half runs about twelve hours; whenever pūrṇimā begins in the morning, bhadrā covers the afternoon and the main rule is blocked.
The fallbacks, in the order the Dharmasindhu gives them: first, tie the rākhī in the pradoṣa after bhadrā has ended, if it ends before the evening; second, if bhadrā runs into the night, take the next morning, provided pūrṇimā is still present for at least the first three muhūrtas after sunrise; third, if even that fails, the bhadrā-puccha on the first day. The afternoon is preferred, the morning is permitted, the bhadrā is refused.
2027, computed
Pūrṇimā begins at 10:29 AM on Monday 16 August and ends at 12:58 PM on Tuesday 17 August — Delhi, this site's engine.
- Monday 16. Aparāhna runs about 1:43 to 4:20 PM (sunrise 5:51, sunset 6:58). Pūrṇimā covers it — but the tithi is twenty-six and a half hours long, so its first half, the bhadrā, runs from 10:29 AM to about 11:43 PM. The afternoon is bhadrā. Blocked. The pradoṣa, 6:58 to about 9:22 PM, is also bhadrā. The first fallback is closed.
- Tuesday 17. Pūrṇimā is present from sunrise at 5:52 AM until 12:58 PM — more than seven hours, far past the three-muhūrta floor. The second fallback is open.
Rakṣā Bandhan 2027, by the nibandha rule: Tuesday 17 August, morning, until 12:58 PM. Not the afternoon, because by the afternoon the tithi has gone; not Monday, because Monday's afternoon and evening are bhadrā. Some households will tie it on Monday after 11:43 PM, in the tail of bhadrā or just past it; the texts allow that as the third fallback, and this page records it without preferring it.
What the rite is
The Bhaviṣya Purāṇa gives a rakṣā-bandhana on Śrāvaṇa pūrṇimā — a protective thread tied by the purohita with a verse naming Bali's binding — and the same pūrṇimā carries the upākarma, the renewal of the sacred thread, in the south. The brother-and-sister form most people mean by the name is later and regional, and it is the form this page's timing serves, because it is the one being asked about. The thread is the constant; who ties it to whom has changed.
Why the times above are not the times for you
Bhadrā is a fixed fraction of the tithi and converts by the time difference. Aparāhna and pradoṣa are measured from your own sun. A city nine and a half hours behind Delhi in August finds the bhadrā ending at about 2:13 PM local on the 16th — inside its own afternoon window — and may have the main rule open where Delhi did not. This site's panchang computes the karaṇa and the windows for the city you type.
What this page does not say
It does not say that a thread tied in bhadrā fails, and it does not say that the morning is second-best in any way that matters. The texts give an order of preference; this page computes where 2027 lands in it and shows the working. What the thread means between two people is not in any nibandha.
Source — Dharmasindhu and Nirnayasindhu on aparahna-vyapini purnima for Raksha Bandhan, on the bhadra prohibition, and on the fallback order (pradosha after bhadra; else the next morning while purnima lasts); the Bhavishya Purana on the rakshabandhana rite; 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.