What is Rahu Kaal?
Rahu Kaal, the period ruled by the shadow planet Rahu, is considered unfavourable for beginnings such as travel, signing deals, or buying property. Routine and ongoing work is unaffected. Because it is derived from the daytime span between sunrise and sunset, it shifts with the seasons and with your location.
Why your city matters
India uses a single timezone across about 30 degrees of longitude, but the sun does not. Every degree of longitude moves sunrise by about four minutes, so Kolkata's sunrise is roughly 80 minutes earlier than Mumbai's on the same calendar day. A single all-India Rahu Kaal from an IST formula is therefore wrong for most cities, and badly wrong abroad in Dubai, London or Toronto. CosmosPandit computes Rahu Kaal from the true sunrise at your exact coordinates, every day.
How it is calculated
Take the daytime length from local sunrise to local sunset, divide it into eight equal parts, and the Rahu Kaal slot is fixed by the weekday. Since sunrise and sunset are computed astronomically for your city, the result is precise rather than a rule of thumb.