When is Diwali (Lakshmi Puja)?

How the date is decided

Diwali is not a fixed calendar date and never has been. It is a rule over the lunar calendar, and this site computes that rule rather than reading a date off a list. Three things have to be true at once:

• the lunar month is Kartik, counted in the purnimanta reckoning;
• the fortnight is Krishna paksha, the waning half;
• the tithi is Amavasya, the fifteenth and last of that fortnight.

The part that decides the civil day is the fourth condition, and it is the one almost nobody publishes: the Amavasya must be running at pradosh — the period just after sunset. This is called the vyapini reference, and each festival has its own. Diwali’s is pradosh because Lakshmi Puja is an evening rite; assigning it to whichever morning happened to begin under Amavasya would put the lamps on a night when the tithi had already ended.

Why the month has two names

If you compare almanacs you will sometimes see Diwali described as falling in Ashwin rather than Kartik. Both are right. Under the amanta convention a lunar month ends at the new moon, so the Amavasya that carries Diwali closes Ashwin. Under the purnimanta convention the month ends at the full moon, so the same Amavasya sits in the middle of Kartik. Gujarat, Maharashtra and most of southern India read the calendar the first way; the north reads it the second.

This site indexes festivals under the purnimanta names, which is why the rule above says Kartik. The dates are identical either way — only the label moves. There is a fuller treatment in amanta and purnimanta.

Why the Gregorian date swings by a month

A lunar month is roughly 29.5 days and a solar year is 365.25, so twelve lunar months fall about eleven days short. Diwali therefore drifts earlier each year until an intercalary month is inserted and it jumps back. The practical range is mid-October to mid-November, and the table above shows the swing across eleven years rather than asserting a single date and leaving you to guess the next one.

The five days are five separate rules

Diwali is the middle of a sequence, and each day in it is judged independently rather than counted off from Diwali:

• Dhanteras — Kartik Krishna Trayodashi, pradosh
• Naraka Chaturdashi — Chaturdashi, pradosh
• Diwali — Amavasya, pradosh
• Govardhan Puja — Kartik Shukla Pratipada, pradosh
• Bhai Dooj — Dwitiya, judged at aparahna instead

Because they are separate rules over tithis of uneven length, the five days are usually but not always five consecutive dates. A tithi that starts and ends between two sunsets can leave a gap, and one that stretches across two can double a day. That is a property of the calendar, not an error in it.

What we do not compute

We fix the day. We do not compute the Lakshmi Puja muhurat within it, the regional Diwali variants observed in Tamil Nadu and Kerala on their own rules, or the choghadiya windows families use to pick a puja time. For that last one, open the choghadiya table for the date and city you care about, or the full panchang for the day itself — sunset, pradosh and the tithi’s exact end time are all there for your own location.