Sri Lanka Rahu Kalaya Calculator — Rahu Kaalam Today

Rahu Kalaya is found with a method that almanacs across Sri Lanka and South Asia share. The daytime — the stretch from sunrise to sunset — is divided into eight equal parts, and each weekday assigns one fixed part to Rahu, one to Yamaganda and one to Gulika. The arithmetic is deterministic; the only input that varies is the day's sunrise and sunset.

1. Resolve sunrise and sunset.For the chosen date and city the tool runs the NOAA Global Monitoring Laboratory solar algorithm: Julian day → solar declination → equation of time → the hour angle for the −0.833° horizon zenith (which accounts for atmospheric refraction and the sun's radius), then converts to Sri Lanka clock time (UTC+5:30). You can override these with almanac figures.
2. Find the day length and segment size. Day length D = sunset − sunrise and each segment is s = D ÷ 8. On a 12-hour day that is 90 minutes; on a 12h30m day it is 93.75 minutes.
3. Locate each segment. Segment k runs from sunrise + (k−1)·s to sunrise + k·s, so the eighth segment closes exactly on sunset.
4. Apply the weekday map. The standard Panchang convention assigns the segments below (counting from sunrise):
   • Sunday — Rahu 8, Yamaganda 5, Gulika 7
   • Monday — Rahu 2, Yamaganda 4, Gulika 6
   • Tuesday — Rahu 7, Yamaganda 3, Gulika 5
   • Wednesday — Rahu 5, Yamaganda 2, Gulika 4
   • Thursday — Rahu 6, Yamaganda 1, Gulika 3
   • Friday — Rahu 4, Yamaganda 7, Gulika 2
   • Saturday — Rahu 3, Yamaganda 6, Gulika 1

The calculator computes each window two ways and confirms they agree: once by adding whole segment lengths from sunrise, and once by taking the exact fraction of the day directly (k ÷ 8 of D). Both routes land on the same minute, which guards against rounding errors in the segment size. The result is a traditional time calculation only — the tool gives windows, never an astrological prediction.

• NOAA Global Monitoring Laboratory — Solar Calculation details (sunrise/sunset method)
• Drik Panchang — Rahu Kaal methodology (8-part weekday convention)
• NOAA Solar Calculator — reference implementation

The solar algorithm and the weekday segment map on this page were last cross-checked on 2026-06-11, with sunrise/sunset validated against published Colombo values. This is a traditional Panchang time calculation, not a government or religious schedule.