Rāma Navamī
The popular claimThe day is fixed to noon, because the text says he was born at noon.
Most festival rules were fixed by the nibandha writers choosing a part of the day. Rāma Navamī's part of the day was chosen for them, by the epic.
What Vālmīki says
The Bāla Kāṇḍa, in the eighteenth sarga, gives the birth: the twelfth month after the sacrifice, Caitra, the ninth tithi, the nakṣatra Punarvasu, five planets exalted, Jupiter with the Moon in Karka rising, and the hour — madhyāhne — the middle of the day. It is one of the very few birth-times in Sanskrit literature stated with tithi, nakṣatra, lagna and hour together, which is why the day's rule follows it so closely.
The rule
Caitra śukla Navamī, taken on the day Navamī is present in the madhyāhna — the third of the five equal parts of daylight, the window around the sun's highest point, a little over two hours long. Where Navamī covers the madhyāhna on two consecutive days, the second is taken; where it covers neither, the day on which it is present in the greater part of the madhyāhna. And where Navamī and Punarvasu coincide at midday, that conjunction is preferred by name, for the reason above.
2027, computed
Navamī begins at 3:24 PM on Wednesday 14 April and ends at 1:21 PM on Thursday 15 April — Delhi, this site's engine.
- Wednesday 14. Sunrise 5:58 AM, sunset 6:45 PM; each fifth of daylight is 153 minutes and the madhyāhna runs 11:05 AM to 1:38 PM. Navamī has not begun. The test fails.
- Thursday 15. Sunrise 5:57, sunset 6:45; madhyāhna 11:04 AM to 1:37 PM. Navamī, which ends at 1:21, covers all but the last sixteen minutes. The test passes.
Rāma Navamī 2027: Thursday 15 April. The Moon is in Puṣya that day, not Punarvasu — Punarvasu was Wednesday — so the nakṣatra preference does not apply this year and the tithi rule alone decides. That is the ordinary case; the conjunction the texts prefer comes round only some years.
The moment within the day
The birth-hour is the muhūrta itself. Tradition fixes the moment of Rāma's birth at the midday muhūrta — the eighth of the fifteen muhūrtas of daylight, called Abhijit — and the pūjā and the reading of the birth passage are timed to it. On the 15th in Delhi, with a day of twelve hours forty-eight minutes, each muhūrta is 51 minutes and Abhijit runs from about 11:55 AM to 12:46 PM. It lies inside the madhyāhna, as it must.
What the epic's line lets us claim, and what it does not
Because Vālmīki gives a tithi, a nakṣatra and a rising sign, it is tempting to run the description backward through an ephemeris and find the year. People have; the results disagree by thousands of years, because the description constrains the sky only loosely, the lagna is a two-hour window, and "five planets exalted" is rarer than it sounds but not unique. This site's own engine can test a candidate date against every clause of the passage, and one of the planned pages under प्रमाण does exactly that, with the misses printed beside the hits. What this page claims is narrower and safe: the festival's midday rule comes from the text, and the text is quoted above.
Why the times above are not the times for you
The madhyāhna is measured from your own sunrise and sunset. In April, Toronto's day is shorter than Delhi's and nine and a half hours behind; the tithi boundary converts, the window does not. This site's panchang computes the madhyāhna for the city you type.
What this page does not say
It does not say that a reading at Abhijit muhūrta produces anything, and it does not say that Navamī observed on the wrong day is unheard. The epic gives a birth-hour; the nibandhas turn it into a rule; the rule is computed here and shown. What the day means to a household is theirs.
Source — Valmiki Ramayana, Bala Kanda 1.18.8–9, for the birth in Chaitra, Navami, Punarvasu, Karka lagna, at midday; Dharmasindhu and Nirnayasindhu on madhyahna-vyapini navami; tithi, nakshatra, 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.