The Tamil Deepavali is the first Krishna Chaturdashi of the solar month Aippasi, on the day it stands at sunrise; the bath is taken before that dawn. Nirnaya Sindhu times the bath by moonrise, then arunodaya. The northern Deepavali is a different day, the Amavasai that holds the evening, for the Lakshmi puja. For the date itself, the printed almanac of your tradition decides. A book's rule explains a date; it does not overrule the almanac.
☕ Three rules, one season
The Ahobila Mutt's almanac sets the Tamil day (Sri Nrisimha Priya, the Ahobila Mutt's almanac, 1982, pp. 18–19). The month is the solar Aippasi, never Purattasi, even in a year with an extra lunar month. The tithi is the first Krishna Chaturdashi of that month, on the day it stands at sunrise. The bath is taken in the last watch of the night before that dawn, so the almanac lists it on the eve.
Nirnaya Sindhu times the Naraka Chaturdashi bath more finely (Nirnaya Sindhu of Kamalakara Bhatta, pp. 147–148). The bath is before sunrise, at moonrise, on the Chaturdashi. If the Chaturdashi holds moonrise on both days, the earlier day; on one day only, that day. Failing moonrise, the day whose arunodaya it holds; arunodaya is 4 nazhigai before sunrise.
The northern Deepavali is the Amavasai, for the Lakshmi puja at pradosha. The book takes the Amavasai that holds pradosha, and the later day when it holds both evenings (Nirnaya Sindhu of Kamalakara Bhatta, p. 149).
At a glance
- Chaturdashi at moonrise before sunrise on both days: the earlier day.
- At moonrise on one day only: that day.
- At moonrise on neither: the day whose arunodaya it holds.
- At neither moonrise nor arunodaya: the Chaturdashi that reaches the last watch of the night; no bath while Trayodashi holds moonrise.
- Chaturdashi gone even at arunodaya: the bath is still taken at arunodaya, the main time.
- Arunodaya: 4 nazhigai (96 minutes) before sunrise.
- What Nava does: Deepavali Pandigai is the first Krishna Chaturdashi of solar Aippasi, on the day it holds sunrise; when it holds no sunrise, the day whose arunodaya it holds, else the day it begins. Pinniravu Naraka Chaturdashi Snanam is the day before. Moonrise is not read, and there is no Amavasai Lakshmi puja day. The last arm, the day Chaturdashi begins, is the Trayodashi-day bath Nirnaya Sindhu refutes; the book takes the Chaturdashi that reaches the night's last watch.
Frequently asked questions
Why is Deepavali in Tamil Nadu a day before the north’s?
The Tamil festival is the Chaturdashi dawn bath; the northern one is the Amavasai evening. When the two tithis fall on different days, so do the festivals.
Can Deepavali fall in Purattasi?
Not by the Mutt’s almanac. It keeps Deepavali in solar Aippasi, even in a year whose lunar month is doubled.
Why is the Naraka Chaturdashi bath listed on the eve?
The bath is in the last watch of the night, before dawn. In the calendar that hour still belongs to the day before.
Deep dive: a Chaturdashi at no sunrise
Sunset 18:00 and sunrise 06:00, so the night's last watch begins at 03:00 and arunodaya at 04:24.
🪔 Begins after one sunrise, ends before the next
Trayodashi holds Monday's sunrise. Chaturdashi begins Monday 07:00 and ends Tuesday 05:00; Amavasai holds Tuesday's sunrise.
- Chaturdashi holds no sunrise, but it does hold Tuesday's arunodaya. Nava's day is Tuesday.
- Had it ended at 04:00, before Tuesday's arunodaya, Nava's day would be Monday, the day it began. Nirnaya Sindhu refuses that day: Monday's dawn is Trayodashi's, and the Chaturdashi reaches the last watch of the night before Tuesday, so the book's bath is before Tuesday's sunrise, and its Deepavali is Tuesday.
🔗 Read first
This page builds on Deepavali and the Ganga snanam, which explains the festival itself.