Rahu Kaal

Rahu Kaal (also spelled Rahu Kalam) is a daily period of approximately 90 minutes considered inauspicious due to the malefic influence of Rahu, the north lunar node. In Vedic astrology, Rahu is a shadow planet (chhaya graha) associated with confusion, deception, and unexpected obstacles. Starting a new activity — a journey, business deal, or ceremony — during Rahu Kaal is traditionally avoided across most of India, especially in South Indian traditions where this observance is particularly strict.

The calculation divides the total daylight duration (sunrise to sunset) into 8 equal segments. Each day of the week assigns Rahu's rulership to a different segment: Monday has Rahu Kaal in the 2nd slot, Saturday in the 3rd, Friday in the 4th, Wednesday in the 5th, Thursday in the 6th, Tuesday in the 7th, and Sunday in the 8th. Because daylight duration varies by latitude and season, the actual clock times of Rahu Kaal shift throughout the year and differ from city to city.

Tithimala computes Rahu Kaal by first determining precise sunrise and sunset times for the user's geographic coordinates using Swiss Ephemeris. The daylight span is divided into eight equal parts, and the appropriate segment is selected based on the weekday. This location-aware computation ensures accuracy whether the user is in Chennai (close to the equator with relatively stable day lengths) or Delhi (with significant seasonal variation).

Beyond Rahu Kaal, the same eight-slot framework also produces Yamaghanta Kaal and Gulika Kaal — two other inauspicious periods associated with different shadow influences. Many users check Rahu Kaal as a quick daily filter before scheduling anything important.