Five days of Diwali, and their tithi anchors

Dhanteras is trayodaśī (त्रयोदशी), the thirteenth lunar day of the waning fortnight. Naraka Chaturdashi is caturdaśī (चतुर्दशी), the fourteenth. Diwali itself is amāvasyā (अमावस्या), the no-moon day the fortnight closes on. Govardhan Puja is pratipadā (प्रतिपदा), the first day of the fortnight that opens next. Bhai Dooj is dvitīyā (द्वितीया), the second.

Five names, five lunar days, not a number missed between them. A tithi (तिथि) is a lunar day, a stage in the widening gap between the moon and the sun rather than a block of clock time. On that showing the festival ought to walk down five dates in a row, one number a morning, and be finished.

Now look at what this November does with it. On the Delhi sheets Dhanteras is Friday the 6th. Naraka Chaturdashi and Diwali are both Sunday the 8th. Govardhan Puja is Tuesday the 10th and Bhai Dooj Wednesday the 11th. Five names, four dates, and a run six days long from the first of them to the last.

The first guess in most houses is that the sheet has slipped, and the second is that the moon has done something peculiar. Neither is so, and the week's own tithi column is the proof.

Trayodashi runs from 10:30 on Friday the 6th to 10:47 on the Saturday. Chaturdashi from 10:47 on Saturday to 11:27 on the Sunday. Amavasya from 11:27 on Sunday to 12:31 on the Monday. Pratipada from 12:31 on Monday to 14:00 on the Tuesday. Dwitiya from 14:00 on Tuesday to 15:53 on the Wednesday.

Sunrise in Delhi that week moves from 06:37 to 06:40, and not one of those six boundaries is anywhere near it. So the naming rule has an easy week of it: ask at sunrise which tithi is running, give the whole day that name, and the tithi column reads straight down the page. The twelfth on Friday, the thirteenth on Saturday, the fourteenth on Sunday, amavasya on Monday, the first on Tuesday, the second on Wednesday. Six mornings, six numbers, nothing repeated and nothing missing.

Five clean lunar days, then, and five festivals that decline to sit on them. What has happened is that the five days are not read at the same hour.

Take them in order, because the order is the surprise. Dhanteras is settled after dark: the trayodashi that counts is the one running in pradoṣa (प्रदोष), the stretch that opens at sunset and runs on about two and a half hours. The fourteenth is settled twice over, in two different parts of one night. Kali Chaudas wants chaturdashi at niśītha (निशीथ), the almanac's true middle of the dark. The oiled bath that gives the same lunar day its other name, abhyaṅga snāna (अभ्यङ्ग स्नान), is taken after the moon has come up and before the sun does, with chaturdashi still running. Diwali goes back to Dhanteras's hour, amavasya running in pradosha. Govardhan Puja is settled in the first hours after sunrise. And Bhai Dooj is settled in the middle of the afternoon, in aparāhṇa (अपराह्ण), the fourth of the five equal parts of the daylight.

Line those up and one festival is being asked about at five separate hours of the day: the middle of the night, the last dark before dawn, the first of the morning, the middle of the afternoon, and twice in the stretch after sunset.

A tithi keeps none of those appointments. It begins where it begins and ends where it ends, and each turn it does so a good deal later on the clock than the turn before. Five fixed questions, one moving answer.

Walking the week

Put the five observances back onto that clean column, one at a time.

Dhanteras is Friday the 6th. Trayodashi began at half past ten that morning and was still running through Friday's pradosha, which the sheet prints as 17:33 to 20:09. By the time Saturday's pradosha came round it had been over for close to seven hours. So Dhanteras falls on the day the tithi column still calls the twelfth, not the thirteenth. Saturday, the day that column does call the thirteenth, ends up with no Dhanteras at all.

Saturday gets the midnight instead. Kali Chaudas is kept that night, in a window the sheet prints as 23:39 to 00:31, and you can check where that came from with a pencil. The sun set at 17:32 and came up again at 06:38, so the dark ran 13 hours and 6 minutes. Cut that into 15 parts and each is a little over 52 minutes long. The eighth of the 15 straddles the true middle of the night, and it runs from 23:39 to 00:31. Chaturdashi was there for all of it.

Sunday the 8th is the crowded one. The oiled bath is taken that morning between 05:41 and 06:38, from moonrise to sunrise, with chaturdashi running until 11:27. Amavasya begins at 11:27, in time for lunch, and is still running when the sun goes down at half past five. So Sunday holds two of the five, Naraka Chaturdashi before breakfast and Diwali after dark, and the sheet prints them on one line without remarking on it.

Monday the 9th then has amavasya at sunrise and no Diwali, for exactly the reason Saturday had trayodashi and no Dhanteras. Amavasya runs out at 12:31, some five hours before Monday's lamps would have gone up.

Govardhan Puja is Tuesday the 10th, in the 2 hours and 10 minutes that open at sunrise, which that morning is 06:40 to 08:50, with pratipada running on until two in the afternoon. Monday morning was still amavasya, so Monday was never in the running.

Bhai Dooj is Wednesday the 11th, and this one you can check as well. Wednesday's daylight runs from 06:40 to 17:29, which is 649 minutes. A fifth of that is a shade under 2 hours and 10 minutes, and the fourth fifth begins three of those after sunrise, at ten past one, and closes at twenty past three. That is what the sheet prints: 13:10 to 15:20. Dwitiya covers the whole of it and does not finish until 15:53. On Tuesday the same window had held only the last 80 minutes of dwitiya, which began at 14:00. Wednesday takes it comfortably.

While the times are in front of you, do one small sum with them. Trayodashi lasted 24 hours and 17 minutes. Chaturdashi 24 and 40. Amavasya 25 and 4, pratipada 25 and 29, dwitiya 25 and 53. Each one is about 24 minutes longer than the one before it. The moon was losing pace all week, and that is why every boundary walks further into the day than the last.

The dates in between

The two dates the headline names stepped over are not blank. Saturday the 7th carries Kali Chaudas. Monday the 9th is the date the sheet itself calls Kartika Amavasya, the no-moon day of the month.

Nor is this year unusual. In 2025 the same pattern ran through October: the 18th, the 20th, the 20th again, the 22nd, the 23rd. In 2027 it will not. The five then fall on the 27th of October through to the 31st, five names on five dates in a row, which is the tidy version everybody assumes is the normal one.

A month boundary hides inside the sequence too, worth knowing before somebody at home uses a month name you did not expect. Where the month is closed at the no-moon night, the first three days are the last of Ashwina and the last two are the first of Kartika, so the festival changes months halfway through. Where the month is closed at the full moon, all five sit inside Kartika. Two households can give the same five days two different month names while looking at the same lamps.

There is a second way the run gains or loses a date, and this series has taken it apart twice already, so I will not do it again here. A tithi long enough to be running at two sunrises in a row has its number printed against two dates, which is the day that happens twice. A tithi short enough to slip between two sunrises collects no date at all, which is the day that never happens. Either can land inside this fortnight, and when one does, the five names shuffle again on top of the shuffling you have just watched.

Monday the 9th is the one to sit with, all the same. It is Kartika Amavasya, the no-moon day of the month itself, printed in the smallest type the page has, and by the time it comes round the lamps have been lit, put out and packed back into their box. A night named for the dark moon, kept the evening before the dark moon's own date.