How this calendar is computed
Every value on this site is calculated from astronomical positions, not copied from a published calendar. Before any release the output is checked against Drik Panchang, the reference most Kerala calendars follow. If a value drifts by more than three minutes the build fails and nothing is published.
What computes what?
| Quantity | Source | Notes |
|---|---|---|
| Malayalam date | kollavarsham | Kollavarsham solar reckoning. Chingam 1 opens the year. |
| Tithi, nakshatra, yoga, karana | mhah-panchang | Lahiri ayanamsa, roughly 24°13′ for this decade. |
| Sunrise and sunset | suncalc | Upper limb with refraction, the standard −0.833° altitude. |
| Rahu, Gulika, Yamagandam | Derived | Eighth parts of the span between sunrise and sunset, assigned by weekday. |
| UK bank holidays | gov.uk | Kept separate for England & Wales, Scotland and Northern Ireland, because they differ. |
Which conventions were chosen, and why?
- The day runs sunrise to sunrise, not midnight to midnight. The headline tithi and nakshatra are the ones in force at sunrise, which is the Kerala convention.
- Handovers are shown, not hidden. “Dwitiya until 08:04, then Tritiya” is what a printed calendar gives you, and the changeover time is usually the thing you actually need.
- Maha Shivaratri is fixed by nishita — the middle of the coming night — not by the tithi at sunrise. In 2026 those two rules fall on different days.
- Kerala festivals are computed at Kochi and shown on the same date everywhere. Onam does not move because you are in Birmingham.
Where can this be wrong?
Being straight about this matters more than looking authoritative:
- Islamic dates are expected, not settled. They are generated from the Umm al-Qura tabular calendar. The observed date is decided by moon sighting and can move a day either way, and UK mosques and Kerala do not always agree. Anything on this site marked “subject to moon sighting” should be confirmed locally.
- Sunrise can differ by a minute or two from another published source, depending on the horizon altitude assumed and the exact coordinates used for a city.
- Elsewhere in the UK is not London. Glasgow's sunrise differs from London's by enough to matter. Use the “Use my location” button on any day page to recompute where you actually are.
- Printed almanacs sometimes disagree with each other on festival dates where a tithi straddles a sunrise. Where that happens, a printed Kerala calendar is the better authority.
Found something wrong?
Tell me and I will check it against Drik and a printed calendar, and either fix it or explain why it stands. Contact Girish Kaitholil.