Rahu Kaal is one of the eight equal parts of the day between sunrise and sunset, roughly 90 minutes long, and it is traditionally avoided for starting anything new. Which of the eight parts it falls on depends only on the weekday; what clock time that part covers depends on your local sunrise and sunset, so it is different for every city and every date.
Rahu Kaal is the one eighth of the daytime that falls to the shadow planet Rahu on a given weekday. Take the interval from sunrise to sunset, divide it into eight equal parts, and the part assigned to that weekday is Rahu Kaal. On a twelve-hour day each part is exactly 90 minutes; on a short winter day it is shorter, and on a long summer day longer.
Nothing about it is a fixed clock time. Two cities in the same time zone whose sunrises differ by half an hour get Rahu Kaal windows half an hour apart, and the same city gets a different window in June than in December. That is why this calculator asks for a city and a date before it prints anything, and computes the true sunrise and sunset for that pair.
The assignment is fixed and does not vary by place: the 8th part on Sunday, the 2nd on Monday, the 7th on Tuesday, the 5th on Wednesday, the 6th on Thursday, the 4th on Friday and the 3rd on Saturday. A mnemonic many almanacs use for that order is Mother Saw Father Wearing The Turban Suddenly.
Worked example. Sunrise 06:00, sunset 18:00, so the day is twelve hours and each of the eight parts is 90 minutes. On a Monday the 2nd part runs 07:30 to 09:00, which is the Rahu Kaal every published panchang gives for that day length. On a Saturday, the 3rd part, it runs 09:00 to 10:30 instead.
The same eight-part division of the day carries two more inauspicious windows. Yamaganda takes the 5th part on Sunday, the 4th on Monday, the 3rd on Tuesday, the 2nd on Wednesday, the 1st on Thursday, the 7th on Friday and the 6th on Saturday. Gulika Kaal takes a plain descending run: the 7th part on Sunday down to the 1st on Saturday.
The three never land on the same part on the same weekday, so an ordinary day carries three separate windows to work around, plus whatever Dur-Muhurtam that weekday adds. In the electional literature all three are absolute exclusion windows for beginning an auspicious act, and none of them carries an attested parihara that would let you use it anyway.
The window shown here is a daytime one, sunrise to sunset. Some traditions extend the same eight-part scheme to the night arc between sunset and the next sunrise; AstroZivi does not compute a night Rahu Kaal, so an evening time judged on this page is judged without that filter.
The page also decides nothing about your chart. Rahu Kaal is a property of the day and the place, identical for everyone standing in the same city, and it uses no birth details at all. For a window chosen against your own horoscope rather than against the calendar, use the muhurta tools linked below.
Divide sunrise to sunset into eight equal parts. Rahu Kaal is the 8th part on Sunday, the 2nd on Monday, the 7th on Tuesday, the 5th on Wednesday, the 6th on Thursday, the 4th on Friday and the 3rd on Saturday. The part number is fixed everywhere; only the clock time changes with your location's sunrise and sunset.
Exactly one eighth of the time between sunrise and sunset. On a twelve-hour day that is 90 minutes. On a nine-hour winter day it is about 67 minutes, and on a fourteen-hour summer day about 105, so the length varies with your latitude and the season as well as the date.
Traditionally, new journeys and new ventures are avoided during Rahu Kaal, while ongoing activities and journeys already begun are considered unaffected. Many people simply avoid starting something important inside the window and carry on with everything already under way.
Two things change. The eighth-part that belongs to Rahu is set by the weekday, and the length and position of each part is set by the day's actual sunrise and sunset at your location. Change either the weekday or the city and the clock window moves.
The Rahu Kaal in common use, and the one this calculator computes, is a daytime period between sunrise and sunset. A night-time division of the same kind exists in some traditions, but it is not computed here, so this page has nothing to say about an hour after sunset.
No. It is derived from local sunrise and sunset, so cities on the same clock but at different longitudes get different windows. Even within one state the start can differ by fifteen to twenty minutes, which is why the calculator is keyed to a city rather than to a time zone.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.