How Rahu Kalam is calculated

Divide the daylight into eight equal parts. One part belongs to Rahu Kalam, and which part depends only on the weekday.

Rahu Kalam comes from local sunrise, local sunset and the weekday. The time from sunrise to sunset is divided into eight equal parts, and a fixed weekday schedule says which part is Rahu Kalam.

A worked example

If sunrise is at 6:12 am and sunset at 6:18 pm, daylight lasts 12 hours 6 minutes. Each eighth lasts 90 minutes 45 seconds. On Monday, Rahu Kalam is the second part, beginning one such interval after sunrise.

The role of Rahu

The name comes from tradition. This calculation uses a weekday schedule; it does not use Rahu's current position in the sky.

Why the time changes

Sunrise, sunset and the length of daylight vary by location and season. Rahu Kalam therefore changes through the year and from city to city, even though the weekday schedule remains the same.

When two calendars differ

A calendar printed for Chennai and one printed for Delhi give different Rahu Kalam times on the same day, because their sunrises differ. Within one city, a minute or two usually comes from how sunrise is defined and how times are rounded.