Understanding Rahu Kalam: Astronomical Basis, Calculation & Spiritual Significance
How the daily 90-minute shadow period is calculated from sunrise to sunset and why major auspicious tasks are paused.
By Panchang Astronomical Board · Updated August 2026
Rahu Kalam is a daily 90-minute period governed by Rahu. Discover how Rahu Kalam is divided into eight equal solar segments, day-by-day timing rules, astronomical principles, and spiritual practices.
What is Rahu Kalam?
In Vedic astronomy and Panchang reckoning, Rahu Kalam (also spelled Rahu Kaal) refers to a specific period of approximately 90 minutes every day that is ruled by Rahu, the northern lunar node. According to traditional astrology, Rahu represents shadow, illusions, and unpredictability. Consequently, commencing new commercial ventures, signing contracts, buying assets, or performing sacred housewarming ceremonies (Griha Pravesh) during this daily window is traditionally avoided.
- Rahu Kalam occurs every single day between local sunrise and sunset.
- Its exact timing changes based on the weekday and local sunrise time of your city.
- Routine daily work and spiritual prayers to Lord Shiva, Goddess Durga, or Rahu remedies can be performed.
How Rahu Kalam is Calculated Astronomy-wise
To compute Rahu Kalam accurately, the daytime interval between local Sunrise and local Sunset is divided into 8 equal time periods (Prahars/Segments). Since daylight on an average 12-hour day equals 720 minutes, each segment spans approximately 90 minutes (1.5 hours). Depending on the weekday, a specific segment out of the 8 is assigned to Rahu:
| Weekday | Solar Segment (out of 8) | Approximate Time (for 6 AM Sunrise) |
|---|---|---|
| Monday | 2nd Segment | 07:30 AM – 09:00 AM |
| Saturday | 3rd Segment | 09:00 AM – 10:30 AM |
| Friday | 4th Segment | 10:30 AM – 12:00 PM |
| Wednesday | 5th Segment | 12:00 PM – 01:30 PM |
| Thursday | 6th Segment | 01:30 PM – 03:00 PM |
| Tuesday | 7th Segment | 03:00 PM – 04:30 PM |
| Sunday | 8th Segment | 04:30 PM – 06:00 PM |
Activities to Avoid and Recommended Spiritual Practices
During Rahu Kalam, it is advised to avoid initiating new business projects, registering property, conducting wedding rituals, or starting long journeys. However, ongoing tasks do not need to be halted. Furthermore, reciting the Rahu Stotram or worshiping Goddess Durga during this period is believed to reduce astrological afflictions.
Frequently Asked Questions
Q: Does Rahu Kalam timing vary by city?
Yes! Rahu Kalam is strictly based on local sunrise and sunset times. For instance, Mumbai sunrise differs from Kolkata or New Delhi, so Rahu Kalam times shift accordingly.
Q: What if an auspicious ritual is already in progress when Rahu Kalam starts?
If a ritual or ceremony (such as a multi-hour Yajna or wedding ceremony) was initiated before Rahu Kalam commenced, it may continue without interruption.