How these dates are computed
The whole method, in public. If you disagree with a rule you can see exactly which one it is — that is the point of publishing this page.
The astronomy
- Ephemeris
- Swiss Ephemeris 2.10.03 (Moshier analytical mode — within about a second of clock time on a tithi boundary, which is invisible at date granularity).
- Zodiac
- Sidereal, Lahiri (Chitrapaksha) ayanamsa — the Indian standard.
- Day boundary
- Local sunrise to the next local sunrise. A date’s tithi and nakshatram are the ones in force at your city’s sunrise.
- Sunrise
- Upper limb of the disc with atmospheric refraction — the standard almanac convention.
- Tamil month
- Begins on the day whose sunset follows the sankranti (the Tamil and Kerala rule). This is what fixes the Aadi and Margazhi boundaries.
- Rahu kalam, yamagandam, gulikai
- The standard eighth-part division of the real local daylight span, not a fixed 6am–6pm table.
- Eclipses
- Solar and umbral lunar eclipses count as grahan. Penumbral lunar eclipses do not — they are invisible to the eye and are not observed as grahan.
The rules
Each occasion has its own written rule list — which nakshatrams are allowed, which tithis and months are avoided — and every rule records where it comes from. The lists are checked against family practice before publication, and where families genuinely differ the page says so rather than pretending there is one answer. The rules are public, so anything you disagree with, you can see and tell us about.
Combustion (moudhyam). Weddings are suspended while Sukra or Guru is combust. We treat a planet as combust inside 10° for Venus (8° when retrograde) and 11° for Jupiter — the conventional muhurtham orbs. Some published lists use a tighter orb and so keep printing dates for a few days after we stop. That is a difference of convention, not of arithmetic: the orb we use is stated here so you can see exactly where our list ends and why.
Where a rule is one families split on — Pournami and Saturday for a wedding, the waning fortnight for a housewarming — the date lists follow the stricter reading, and the looser one is offered as a switch on the page itself. Turning it on adds dates, each marked optional. Nothing is hidden either way: both readings are in the published rule files, with the reason for each.
| Occasion | What the rule set does |
|---|---|
| Engagement / nichayathartham | Dates for a nichayathartham. The rules are looser than the wedding's — the month blocks and combustion periods still apply, but the nakshatra list is wider and Saturday is not excluded. |
| Griha pravesam (housewarming) | Dates for entering a new home. The fixed and soft nakshatras are preferred, the growing (shukla) fortnight is preferred, and the same three months are avoided. Diaspora note: closing dates rarely bend, so the list is deliberately wider than the wedding's. |
| Seemantham / valaikappu | Dates for a seemantham or valaikappu. Traditionally held in the fifth, seventh or ninth month of pregnancy, so the window is fixed by the pregnancy and the family picks the best date inside it — use the month filter on the page rather than reading the whole year. |
| New venture / shop opening | Dates for opening a shop, office or business. The chara (movable) and kshipra (swift) nakshatras are preferred — the traditional reasoning is that a venture wants momentum, the opposite of the fixed nakshatras you want for a house. |
| Wedding muhurtham | Dates a Tamil family would normally consider for a wedding, computed at your city's sunrise. The strictest of the five lists — three whole months, both planetary combustion periods and the rikta tithis are excluded, so a thin year is a correct result, not a broken one. |
Cross-checking
Every published year is sampled (n=40, all cities, both years) and each sample’s tithi and nakshatram checked against two independent panchangam sources. All 40 agreed on both elements. The full report — including the sources, the sunrise differences between them, and what has not been checked — is in the public pipeline repository.
One limit worth stating here rather than burying: both sources compute by drik-ganita, as we do. That confirms the arithmetic. It does not test these dates against a printed vakya almanac, which is the check that could genuinely disagree, and it is still outstanding.
What this is not
No horoscope matching, no jathagam porutham, no personalised prediction. This is a shortlisting tool: it narrows a year to the dates worth discussing.
These are dates a family would normally consider — confirm the final date and the muhurtham time with your family purohit.