Rahu Kaal

What is Rahu Kaal?

Rahu Kaal (also spelled Rahu Kalam) is a recurring period of roughly one and a half hours each day, considered inauspicious in Vedic astrology for beginning anything important — travel, signing agreements, ceremonies, a new venture. It is attributed to Rahu, the north lunar node.

Unlike a festival or a tithi, Rahu Kaal is not astronomical in the usual sense: it is purely a division of daylight. It depends only on the weekday and your local sunrise and sunset, which is why it lands at a different clock time every day and in every city — and why no single “Rahu Kaal time” is correct for everyone.

How Rahu Kaal is calculated

The rule is simple and exact:

1. Take the daylight span, sunrise to sunset, and divide it into eight equal parts.
2. Each weekday assigns Rahu to one of those eight parts.

The weekday-to-part rule is fixed. Counting the eighths from sunrise:

The right-hand column is only an illustration for a tidy 12-hour day, where each eighth is 90 minutes. On a real day the parts are one-eighth of the actual daylight, so they stretch in summer and compress in winter, and shift with your city’s sunrise.

A worked example — Thursday in a city with sunrise 06:00, sunset 18:00

Daylight is 12 hours, so each eighth is 12 h ÷ 8 = 90 minutes. Numbering from sunrise: part 1 is 06:00–07:30, part 2 is 07:30–09:00, and so on. Thursday’s Rahu Kaal is the 6th part:

06:00 + (90 min × 5) = 13:30, ending 90 minutes later at 15:00.

Move the same Thursday to a summer city where the day runs 05:30 to 19:30 (14 hours), and each eighth becomes 105 minutes — so Rahu Kaal shifts to roughly 14:15–16:00. Same weekday, same rule, different clock, because the daylight is longer. This is exactly why AstroShruti computes it from your city’s true sunrise and sunset rather than printing a fixed time.

Rahu Kaal, Yamaganda and Gulika

Rahu Kaal is one of three inauspicious daylight windows built the same way — each a different eighth of the day, by weekday:

Rahu Kaal and Yamaganda are daytime-only. Gulika Kaal is the exception: it also has a night window (the night, sunset to next sunrise, split into eight, with Gulika on its own part). Gulika — associated with Saturn’s son — is often treated as the most cautionary of the three for beginnings, while Rahu Kaal is simply the most famous.

What to avoid — and what is fine

• Avoid starting: a new job, a journey, a purchase of consequence, a wedding ritual, an important meeting, a new venture.
• Not affected: anything already under way — a journey in progress, ongoing work, routine tasks.
• Often considered fine: remedial or devotional worship; many traditions regard prayer during Rahu Kaal as acceptable or even apt.

If an auspicious act cannot avoid the window, the usual advice is to move it out of the window entirely, not to time it to a “less bad” minute — tradition treats the whole stretch, not a point inside it.

Common mistakes

• Believing Rahu Kaal is a fixed clock time (like “always 4:30–6:00 pm”). It is a fraction of daylight; the clock time moves daily and by city.
• Getting the weekday mnemonic backwards. Monday is the 2nd eighth (mid to late morning), not the last; Sunday is the 8th (late afternoon). Use the table above.
• Cancelling a trip already begun. The prohibition is about starting; a journey under way is not affected.
• Reading Rahu Kaal in isolation. A good choghadiya or hora still has to clear Rahu Kaal, and vice versa — they are separate checks that must agree.

What AstroShruti computes — and what it doesn’t

AstroShruti computes Rahu Kaal, Yamaganda and Gulika from your city’s true local sunrise and sunset — eight equal parts, the weekday’s assigned part, the exact start and end — plus Gulika’s night window, all from the same engine that drives the charts. It also flags where these overlap a Choghadiya, Hora or Gowri slot on those tables.

What it does not do is grade the window internally or promise a consequence. There is no “worst minute” calculation, and the software never claims that acting in Rahu Kaal will cause a specific harm — only that tradition avoids it for beginnings. It gives you the exact window so the decision to work around it is yours to make.

Related concepts

• Choghadiya — the eight quick slots; cross-check every good one against Rahu Kaal.
• Hora — the planetary hour; a good hora inside Rahu Kaal is still compromised.
• Gowri Panchangam — the Tamil table whose Visham period is Rahu Kaal under another name.
• Vara — the weekday that fixes which eighth of the day Rahu Kaal falls in.