Rahu Kalam

What rahu kalam is, and how it is calculated

Rahu kalam is the portion of the day associated with Rahu, the ascending lunar node. It is not a planet in the physical sense — Rahu and Ketu are the two points where the moon's orbit crosses the ecliptic — and the tradition treats the period named for it as a stretch of the day best left to routine rather than to beginnings.

The daylight period — sunrise to sunset — is divided into eight equal parts, and one of them is assigned to this window by the day of the week. Because the parts are fractions of daylight rather than fixed clock hours, each one stretches in summer and contracts in winter, and each falls at a different clock time in every city. A window that runs 90 minutes in June may run 75 in December, and Hyderabad's will not be Delhi's.

The assignment is fixed and does not vary by region: Sunday takes the eighth part, Monday the second, Tuesday the seventh, Wednesday the fifth, Thursday the sixth, Friday the fourth and Saturday the third. This is why rahu kalam appears to move backwards and forwards through the day across a week rather than sliding steadily — the sequence is an order of assignment, not a progression through the clock.

What it is used for is narrower than its reputation suggests. Families who observe it avoid starting something new inside the window — signing an agreement, setting out on a journey, beginning a ceremony. Work already under way continues; nobody is expected to stop. It is a scheduling convention, followed closely by some households and lightly by others, and it carries no claim about what will happen to anyone who ignores it.

Because it is derived entirely from sunrise and sunset, the window on this page is computed for the city in the header. Change the city and every timing moves with it — a printed panchangam calculated for a different place will give a different answer, and neither is wrong.

Counted from sunrise. On a twelve-hour day each eighth is ninety minutes; on a shorter winter day it is less.