✦ Karthigai Days ✦

✦ Monthly Krittika nakshatra days — sacred to Lord Murugan ✦

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✦ What is Karthigai Days? ✦

Karthigai (Tamil) or Krittika is the third nakshatra in Vedic astronomy — known to modern astronomy as the Pleiades cluster. In Tamil tradition, when the Moon transits Krittika each month, that day is called "Karthigai Day" — sacred to Lord Murugan (Kartikeya).

Monthly Karthigai occurs 12 times a year. On this day, Tamil devotees worship Lord Murugan, light deepams, and perform agni-homa. Some observe fasts.

The most famous is "Karthigai Deepam" — celebrated on the Purnima of the Tamil month "Karthigai" (typically Nov–Dec) when it coincides with Krittika nakshatra — South India's "Diwali-equivalent" festival of lights. At Tiruvannamalai's Arunachaleshwar temple, a massive lamp is lit on the mountain peak.

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✦ Concept & Rule ✦

Astronomical basis: Krittika nakshatra (index 3) spans 26°40' Aries to 10° Taurus (sidereal). The Moon spends ~24 hours in each nakshatra, so monthly Karthigai is a single day. The day at sunrise of which Krittika is active is "Karthigai Day". The Tamil month "Karthigai" is the 8th of the year (begins ~mid-November); the Purnima-Krittika day in that month = "Karthigai Deepam".