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.

Sunrise is the anchor, not the clock

The one number that moves everything is sunrise. Shift sunrise by ten minutes and all eight segment boundaries shift with it, because every boundary is measured forward from sunrise rather than from a fixed clock hour. That is why a printed "Rahu Kalaya 9.00 to 10.30" table is only an approximation: it assumes a 6 am to 6 pm day that Sri Lanka rarely gets exactly. If you want to see the raw inputs for your own town, the Sri Lanka sunrise and sunset times tool prints the same solar figures this calculator feeds on, including day length and solar noon.

Why the window is rarely exactly 90 minutes

Ninety minutes is the number people remember, and it is only true on a day that is exactly twelve hours long. Sri Lanka sits close to the equator, so day length is stable compared with Europe, but it still swings by roughly 48 minutes across the year. In Colombo during 2026 the computed day length runs from about 703 minutes in mid December to about 751 minutes in mid June. Divide by eight and the segment length, which is also the length of Rahu Kalaya, runs from about 1 h 28 min to about 1 h 34 min. A window printed as a flat 90 minutes is therefore up to three minutes wrong at each end for half the year.

Why your city matters by a few minutes

Two things separate one Sri Lankan town from another. Longitude sets when the sun crosses the local meridian, and the whole island shares one clock (UTC+5:30), so eastern towns see the sun earlier. Latitude changes how long the sun stays up, which changes the segment length. On 18 October 2026, a Sunday, the Rahu window opened at 16:17 in Batticaloa, 16:21 in Kandy, 16:23 in Jaffna and 16:25 in Colombo and Negombo. Eight minutes is small, but it is larger than the rounding anyone argues about when two almanacs disagree.

Edge cases the calculator handles

• Segment 8 closes exactly on sunset. Boundaries are built as multiples of the exact segment length, so the eighth window ends on the computed sunset minute with no off-by-one overrun.
• Manual override validation. Enter a sunset at or before sunrise and the tool refuses with "Sunset must be later than sunrise" instead of printing negative windows. Leave one field blank and it asks for both.
• Impossible calendar dates. A date such as 30 February is round-tripped through the calendar and rejected, so it can never silently become 2 March.
• Date range limits. Years outside 1950 to 2100 are refused rather than extrapolated, keeping the solar model inside its tested span.
• No-sunrise latitudes. If the hour-angle cosine falls outside the range −1 to +1, meaning polar day or polar night, the tool returns an error instead of a nonsense window. This never happens in Sri Lanka, but the guard means the module stays honest if the coordinates ever change.
• Timezone independence. The weekday comes from the calendar date computed in UTC, so a browser set to New York still reports the Sri Lankan weekday for 15 June 2026, which is a Monday everywhere.

What this tool does not do

It gives time windows and nothing else. There is no reading of your chart, no verdict on whether a plan will succeed, and no claim that the tradition has a physical effect. Rahu Kalaya, Yamaganda and Gulika are daytime windows only; the night-time equivalents used by some almanacs are a separate convention and are out of scope. For horoscope casting, which needs a birth time and place rather than a date, see the Sri Lanka birth chart and lagna calculator. For the fixed auspicious times published once a year for the Sinhala and Tamil New Year, the New Year nekath times page carries the gazetted list rather than a computed one.

This is the table most printed almanacs show: the eight segments of a nominal 6 am to 6 pm day, 90 minutes each, with the segment each weekday assigns to Rahu, Yamaganda and Gulika. Use it as a quick mental check. For the real minutes on a real date, use the calculator above, which cuts the segments from actual sunrise and sunset instead of assuming a 6 to 6 day.

Read the pattern rather than the clock times: Rahu moves to the last segment on Sunday and the second on Monday, Yamaganda takes the first segment on Thursday, and Gulika takes the first on Saturday. Those assignments never change. Only the minutes attached to them do.

Below are the computed figures for Colombo on the 15th of each month in 2026, taken straight from the same solar routine the calculator uses. Sunrise and sunset repeat to within a minute or two from year to year, so the shape of this table holds for any year. The right-hand column is the length of Rahu Kalaya, Yamaganda and Gulika on that day, since all three are one eighth of the daytime.

The shortest windows fall around the December solstice and the longest around the June solstice, a spread of about six minutes. Sunrise itself moves more than day length does, by roughly half an hour between mid June and mid January, which is why the start of a morning Rahu window can look half an hour out if you reuse an old printed table.

Most people who look this up are not studying astronomy, they are picking a time for something that happens once: handing over a shop key, starting a journey, filing papers, cutting a ribbon. Three practical habits cover almost every case.

1. Fix the start, not the whole event. The tradition concerns beginnings. If Rahu Kalaya ends at 09:00, families commonly set the formal start at 09:05 and let everything else run on normally. An event already under way is usually left alone.
2. Check the weekday before you fix the date. Because the assignment is fixed per weekday, a Thursday puts Yamaganda in the very first segment, straight after sunrise, while a Saturday puts Gulika there. If you want a clear early morning, Monday, Tuesday and Wednesday keep segment one free.
3. Line the date up with the rest of the calendar. A date that dodges Rahu Kalaya is no use if the registry is shut. The Sri Lanka public holidays calendar lists the gazetted days, and the moon phase and Poya calendar shows the Poya dates that shift year to year. For a wedding, the marriage registration fee calculator covers what the registrar will charge once the date is settled.

One more point worth stating plainly: Poya days, public holidays and full moons do not change Rahu Kalaya at all. The calculation only reads the weekday and the day's sunrise and sunset, so a Poya that falls on a Tuesday carries exactly the Tuesday assignment, segment 7 for Rahu. Nothing in the method treats a holiday differently.

• 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 2026-10-18, with sunrise/sunset validated against published Colombo values. This is a traditional Panchang time calculation, not a government or religious schedule.