Rahu Kalam (ராகு காலம், also spelled Rahu Kaal or Rahu Kala) is a daily inauspicious period of approximately 90 minutes in the Hindu Panchang, governed by Rahu — the ascending node of the Moon in Vedic astrology. Rahu is one of the nine Navagrahas and is associated with karmic challenges, sudden changes, and the unpredictable. The period is widely observed throughout South India and by Tamil, Telugu, Kannada, and Malayalam communities worldwide.
The traditional advice is to avoid starting new activities during Rahu Kalam: new business ventures, signing contracts, beginning travel, conducting ceremonies, making investments, or performing auspicious rituals. Activities already in progress are generally considered unaffected — only the initiation of something new is avoided. In some traditions, Rahu Kalam is actually considered auspicious for worship of Rahu and for prayers related to ancestral souls (Pitru Puja).
Rahu Kalam is calculated from the local sunrise time for each day. The period from sunrise to sunset is divided into 8 equal octaves. Rahu Kalam occupies one of these octaves, and which octave depends on the day of the week: Sunday=8th, Monday=2nd, Tuesday=7th, Wednesday=5th, Thursday=6th, Friday=4th, Saturday=3rd. The result is that the exact clock time of Rahu Kalam is different every day and in every city.
A common approximation (for a 6 AM sunrise) gives rough times: Monday 7:30–9 AM, Tuesday 3–4:30 PM, Wednesday 12–1:30 PM, Thursday 1:30–3 PM, Friday 10:30 AM–12 PM, Saturday 9–10:30 AM, Sunday 4:30–6 PM. In practice, these times shift by 15–90 minutes depending on your location and the time of year.
The three main inauspicious periods in South Indian Panchang tradition are Rahu Kalam, Yamagandam (associated with Yama), and Kuligai Kalam (Gulika, associated with Saturn). Of these, Rahu Kalam is the most widely observed and is prominently listed in all daily Panchangams and calendar apps.