Rahu Kalam (also spelled Rahu Kaal, Rahu Kala, Rahukalam, Rahukaalam) is the most important inauspicious period in Hindu astrology, observed daily across India. It occurs every day for approximately 90 minutes and is calculated by dividing the daylight period (sunrise to sunset) into eight equal parts, with each weekday having a specific part designated as Rahu Kalam.

Puranic Origin: The Garuḍa Purāṇa directly states that those under hostile planetary influence should perform Grahayajña (planetary propitiation). According to mythology, Rahu was the demon Svarbhanu who disguised himself as a god during the Samudra Manthan (churning of the cosmic ocean) to drink the Amrita (nectar of immortality). Lord Vishnu severed his head with the Sudarshana Chakra before the nectar could pass his throat. The severed head became Rahu (north lunar node) and the body became Ketu (south lunar node). Rahu eternally seeks revenge on the Sun and Moon who exposed his disguise, causing eclipses.

Calculation Method: The time between sunrise and sunset is divided into 8 equal segments (~90 min each). The specific segment that becomes Rahu Kalam follows a weekday pattern: Sunday=8th, Monday=2nd, Tuesday=7th, Wednesday=5th, Thursday=6th, Friday=4th, Saturday=3rd. Since sunrise varies by location and season, Rahu Kalam timings for Delhi are calculated fresh each day.

Why Shiva Worship During Rahu Kalam? This is supported by ancient tradition! Lord Shiva as Nilakantha (blue-throated one) consumed the world's poison during Samudra Manthan — he alone can neutralize Rahu's malefic energy. On Mondays specifically, Shiva worship during Rahu Kalam gives double benefit: removing Rahu dosha AND fulfilling the Somavāra-vrata merit (Skanda Purāṇa directly mandates Shiva worship on Mondays). The famous Srikalahasti temple (premier Rahu-Ketu temple) performs Rahu-Ketu puja from 6 AM to 6 PM — spanning the entire day including Rahu Kalam.

What Can Be Done: Ongoing work can continue. Shiva puja, Rahu mantra chanting, Navagraha prayers, Pitru Tarpan (ancestral offerings), meditation and spiritual practice are all suitable or even especially powerful during Rahu Kalam.