Rahu Kaal today: the computation and a calculator
Rahu Kaal is asked about millions of times a day and almost never explained as what it is: a fixed convention laid over deterministic astronomy. Sunrise and sunset are physics. Dividing the day into eight parts is arithmetic. Assigning one part to Rahu by weekday is tradition. This page spells out the full computation, explains why the window moves with city and season, and carries a calculator that runs the whole thing in your browser.
What Rahu Kaal is
In muhurta, the Vedic discipline of choosing start times, each day carries a set of recurring windows judged favourable or unfavourable for beginnings. Rahu Kaal (also written Rahu Kalam or Rahukalam) is the most widely observed of the unfavourable ones: a stretch of roughly ninety minutes, one-eighth of the time the sun is above the horizon, assigned to Rahu, the shadow node that has no physical body but a long career in the tradition's timing rules. Convention says do not start new undertakings in this window: no business openings, no journeys, no signings. It sits alongside two sibling windows, Yamagandam and Gulika Kalam, which use the same eight-segment machinery with different weekday assignments; the three are compared in Rahukalam, Yamagandam and Gulika.
It is worth being precise about what kind of object this is. Rahu Kaal is not an astronomical event. Nothing happens in the sky at its boundaries. It is a bookkeeping rule applied to two genuine astronomical events, sunrise and sunset, and its entire content is the rule. That cuts both ways: it means the window can be computed exactly, for any place and date, centuries forward or backward, and it also means the question "does it work" is a question about the convention, not about the astronomy. Rahu itself does participate in structural work elsewhere on this site, from the Rahu mahadasha to the Rahu and Ketu transit cycle to the nakshatras Rahu rules. Those are slow-cycle techniques; Rahu Kaal is an intraday convention that borrows the name.
The exact computation
The full algorithm fits in four steps.
- Compute sunrise and sunset for the location and date. This is the only genuinely astronomical step, and it is solved physics: solar position algorithms such as NOAA's give the times to within a minute or two.
- Take the daylight span: sunset minus sunrise.
- Divide by eight. The eight equal segments are counted from sunrise: segment 1 starts at sunrise, segment 8 ends at sunset.
- Pick the weekday's segment. The assignment is fixed: Sunday takes the 8th segment, Monday the 2nd, Tuesday the 7th, Wednesday the 5th, Thursday the 6th, Friday the 4th and Saturday the 3rd.
| Weekday | Rahu Kaal segment | On a 6:00 to 18:00 day |
|---|---|---|
| Sunday | 8th | 16:30 to 18:00 |
| Monday | 2nd | 7:30 to 9:00 |
| Tuesday | 7th | 15:00 to 16:30 |
| Wednesday | 5th | 12:00 to 13:30 |
| Thursday | 6th | 13:30 to 15:00 |
| Friday | 4th | 10:30 to 12:00 |
| Saturday | 3rd | 9:00 to 10:30 |
The third column shows the idealised equinox-at-the-equator case where every segment is exactly 90 minutes. Real days are not that tidy, which is the next section.
Why the window moves with city and season
Everything in the computation hangs off two local quantities, sunrise and sunset, and both move. Longitude shifts the whole day earlier or later: Kolkata's sun rises well before Mumbai's even though both run on Indian Standard Time, so Kolkata's Rahu Kaal sits earlier on the clock. Latitude and season change the length of the day: in Delhi the daylight span swings from roughly ten hours in December to fourteen in June, so each one-eighth segment swells from about 75 minutes to about 105, and the segments far from midday slide around accordingly. Go far enough north, to London or Toronto, and the seasonal swing gets larger still; go past the polar circles and there are dates with no sunrise or sunset at all, on which the eight-segment rule has nothing to divide and simply does not apply.
The practical consequence: a printed all-India Rahu Kaal table is an approximation, and a window copied from a different city can be off by half an hour or more. If the convention matters to you, compute it for your coordinates and date. That is what the calculator below does.
The calculator
Implementation notes, honestly stated: sunrise and sunset come from the standard NOAA solar position algorithm implemented inline (no libraries, no network requests), using the conventional zenith of 90.833°, which corresponds to the sun's upper limb touching the horizon with standard atmospheric refraction. Expected accuracy is within a minute or two of observatory tables for non-polar latitudes. Times are rendered in the selected city's own time zone via the browser's IANA time zone database, so your device's zone does not corrupt the output; the "use my location" path uses your device's zone. Segment order follows the pan-Indian convention given above; some regional almanacs assign the weekday segments slightly differently, and panchanga sunrise definitions (disc centre, no refraction) can differ from ours by a few minutes. The computation is deterministic; the convention is the convention.
What Tempora does and does not do with it
Tempora publishes this page for one reason: the computation is deterministic astronomy plus a fixed rule, and publishing it transparently beats leaving readers to opaque tables. That is the same instinct behind the rest of the muhurta cluster, from business launch timing to wedding date selection to Choghadiya, the other major intraday segment system.
What Tempora does not do is use Rahu Kaal in its market research. The firm's working layers are slow-cycle: dashas (see which dasha system), sign-level transits such as Sade Sati, and backtests scored against base rates in the manner described in calibrated lift. Rahu Kaal has not been through that machinery, here or anywhere we know of. So the honest status report is: there is no calibrated public evidence that beginnings inside the window fare worse than beginnings outside it, and equally no calibrated evidence that they fare the same. Absence of evidence in both directions. We will not tell you the window works, because we cannot show that, and we will not mock a convention observed by hundreds of millions of people as costless superstition, because "costless" and "untested" are claims too. If you observe it, this page gives you exact times. If you do not, nothing here says you should start.
Where Tempora does take dated positions, they are on the Tracker with written test conditions, and the exploratory work that has not earned a scoreboard entry sits on the Lab. If you want your own chart's timing layers computed with the same engine used across this site, that is Kaal.
Frequently asked
What is Rahu Kaal?
Rahu Kaal (also written Rahu Kalam or Rahukalam) is a daily window in muhurta practice that convention marks as inauspicious for starting new undertakings. It is defined as one-eighth of the daylight span, the time between sunrise and sunset, with the specific eighth determined by the day of the week. It is a convention layered on top of deterministic astronomy: the sunrise and sunset are physics, the assignment of one segment to Rahu is tradition.
How is Rahu Kaal calculated?
Take sunset minus sunrise for the location and date to get the daylight span. Divide it by eight to get eight equal segments, counted from sunrise. The Rahu Kaal segment by weekday is: Sunday the 8th segment, Monday the 2nd, Tuesday the 7th, Wednesday the 5th, Thursday the 6th, Friday the 4th and Saturday the 3rd. On a day with a 6:00 sunrise and 18:00 sunset each segment is exactly 90 minutes and Monday's Rahu Kaal runs 7:30 to 9:00; on real dates the segments stretch or shrink with the daylight.
Is Rahu Kaal the same in every city?
No. The window depends on local sunrise and sunset, which depend on longitude, latitude and season. Two cities in the same time zone can have Rahu Kaal windows tens of minutes apart, and the same city's window drifts through the year as days lengthen and shorten. This is why printed one-size tables are approximations and why the calculator on this page computes the window per city and date.
Should I avoid starting things during Rahu Kaal?
That is a personal call, not an empirical instruction. The tradition says avoid beginnings in this window; there is no calibrated public evidence that outcomes differ for actions started inside versus outside it, in either direction. Tempora publishes the computation because it is deterministic and frequently asked for, and does not use Rahu Kaal in its own market research. If observing the convention costs you little and lowers anxiety, that is a reasonable trade; treating it as a hard operational constraint has no measured basis we can point to.
Does Tempora use Rahu Kaal in its research?
No. Tempora's market and event research runs on slow-cycle work such as dashas, sign-level transits and calibrated backtests, and its dated forward calls live on the public Tracker with test conditions. Rahu Kaal is an intraday convention that has not been through any calibration here, so it carries no weight in that work. The page exists because the computation is deterministic astronomy plus a fixed rule, which is exactly the kind of thing worth publishing transparently.
Why does Rahu Kaal change every day?
Two reasons. First, the weekday rule moves the assigned segment: the 2nd segment on Monday, the 7th on Tuesday and so on, which shifts the window by hours between consecutive days. Second, sunrise and sunset themselves drift daily with the season, so even the same weekday's window differs week to week. Both effects are fully predictable; nothing about the window's movement is mysterious.
Read next
This page documents a traditional muhurta convention and provides a deterministic computation of it. Publication is not endorsement: Tempora does not use Rahu Kaal in its research and knows of no calibrated evidence for or against the convention. Calculator times are computed client-side with the NOAA solar position algorithm and are accurate to within a minute or two at non-polar latitudes; panchanga conventions may differ by a few minutes. Nothing here is financial, medical, legal or personal advice. First published 10 July 2026 by Tempora Research.