The general Karthigai Deepam is the evening in the bright half of the solar month Karthigai when the Krithikai star holds at sunset or soon after. Kalaprakasika makes the Full Moon the festival's mark instead, and the Sri Vaishnava Pancharatra Deepam follows the Full Moon. So the two lamp days can be a day apart. For the date itself, the printed almanac of your tradition decides. A book's rule explains a date; it does not overrule the almanac.
☕ The star evening and the Full Moon
The festival's moment is the evening, when lamps are lit. Kalaprakasika says: “The appropriate time for illumination is about sunset”, then twilight, and “No illumination should be started later.” (Kalaprakasika (tr. N. P. Subramania Iyer, 1917), ch. XLIV, pp. 239–240).
The general day follows the Krithikai star: the evening in the bright half of the month when Krithikai holds.
Kalaprakasika reads the festival from the Full Moon instead: “The Full-Moon is the fundamental significator of this festival”, whichever star is running. The Sri Vaishnava Pancharatra Deepam keeps that Full-Moon rule.
For two candidates the book takes the later: of two evenings with the Full Moon, the second, and “If two Pournamis occur during the month, then also the second should be chosen.”
At a glance
- General: solar Karthigai, bright half, the Krithikai star at sunset or by the end of the evening window.
- Pancharatra: the Full Moon of Karthigai in the afternoon; a day touched by Chaturdashi at sunrise is passed over for the next.
- Lamp time for both: about sunset, then twilight; no lighting begun later.
- What Nava does: Karthigai Deepam is the evening in the bright half of solar Karthigai when Krithikai holds at sunset or at the end of the pradosha kala, 90 minutes after sunset. When Krithikai holds two such evenings, both are given. Sri Pancharatra Deepam is the day the Full Moon holds the afternoon in Karthigai; when Chaturdashi holds that day's sunrise, it moves to the next day, and when the Full Moon holds no afternoon, it is the day the Full Moon holds sunrise.
Frequently asked questions
Why are there two Karthigai Deepam days in some years?
One rule follows the Krithikai star and the other the Full Moon. The star and the Full Moon can sit on different evenings, and then the two rules give different days.
What if Krithikai holds on two evenings?
Then both evenings qualify under the star rule. Nava gives both; your temple or almanac says which one it keeps.
When should the lamps be lit?
About sunset, then through the twilight. Kalaprakasika says no lighting should be begun later than that.
Deep dive: when the star and the Full Moon part
A sample year in the bright half of Karthigai.
🪔 Two evenings
Monday evening: Krithikai holds at sunset; the tithi is Chaturdashi, and the Full Moon begins late that night. Tuesday: the Full Moon holds the afternoon; the star has moved on to Rohini.
- The general Karthigai Deepam is Monday, the Krithikai evening.
- The Pancharatra Deepam is Tuesday, the Full-Moon day.
🔗 Read first
This page builds on Karthigai Deepam, which explains the festival itself.