Many people remember Rahu Kaal as "Monday 7:30 to 9:00". That table is only right on a day when the Sun rises at exactly six and sets at exactly six. Everywhere else, and in every other season, the window shifts.
The rule
Take the time from sunrise to sunset at your location and divide it into eight equal parts. Rahu Kaal is one of those parts, chosen by weekday: the eighth on Sunday, the second on Monday, the seventh on Tuesday, the fifth on Wednesday, the sixth on Thursday, the fourth on Friday and the third on Saturday. A Bengaluru winter day of about eleven hours and forty minutes gives parts of roughly 87 minutes, not 90.
Why sunrise is the hard part
The rule is trivial; the sunrise is not. The engine needs your latitude, longitude and time zone, then finds the moment the Sun's upper limb touches the horizon with atmospheric refraction included. Jyotish Drishti takes these from the Swiss Ephemeris routines, the same source it uses for planetary positions, so the Panchang and the Rahu Kaal tool always agree with each other.
Yamaganda and Gulika
The same eight-part division gives two sibling windows, Yamaganda and Gulika Kaal, with their own weekday tables. Traditional practice avoids starting new work in Rahu Kaal and Yamaganda, while Gulika is treated as more neutral. The Rahu Kaal page lists all three for the day and the week.
Try it on Jyotish Drishti
Today's Rahu Kaal for your city →