Diwali is held on the new-moon night of the Hindu month of Kartik, and Hindu months follow the moon, not the Gregorian calendar. A year of twelve lunar months is about 11 days shorter than a solar year, so the date slides earlier each year. Every couple of years an extra month is added, and it jumps back. That keeps it somewhere between mid-October and mid-November.
The moon sets the day
The Hindu calendar is lunisolar. Its months are counted by the moon's phases, and the year is kept in step with the seasons. Diwali falls on amavasya, the new-moon night, when the sky is darkest. That's the point of the lamps.
Different regions count the months from different points, so the same night is called Kartik in some calendars and the last night of Ashvin in others. It's the same night either way.
Why it moves earlier each year
A lunar month lasts about 29.5 days, so twelve of them make about 354 days. A solar year is about 365. The gap is the 11 days, and a festival tied to the moon slips back by about that much against the Gregorian calendar.
You can see it in the table this site works from. In 2026, Lakshmi Puja is Sunday 8 November. In 2027, it's Friday 29 October, 10 days earlier on the calendar.
Why it jumps back
If the slide never stopped, Diwali would drift round every season. It doesn't, because the calendar adds an extra month, called adhik maas, about every two to three years. That puts the festival back in the autumn, and the date jumps later by roughly a month.
Why two calendars can disagree by a day
A tithi, or lunar day, isn't tied to midnight. It starts and ends at whatever moment the moon reaches a certain angle, so the new-moon tithi can begin on one afternoon and end the next. That means it can span two evenings.
Lakshmi Puja is done in the evening, in the twilight called Pradosh, so panchangs look for the evening when the new-moon tithi is running. When it covers both, most go with the first. But local sunset times and calculation methods differ, so a calendar for Mumbai and a calendar for a city in the US can sometimes give different days.
In 2025, for example, news reports and calendars were split between 20 and 21 October. Nobody was wrong. They were reading the same tithi against different evenings.
What this means when you're sending a wish
If your family or your temple follows a particular panchang, trust it. The date this site prints is the one most calendars follow. Where sources split, the festival calendar marks it with "around".
For the message itself, a day either way doesn't matter. A wish sent the day before or the day after still lands, and the Diwali wishes page has lines for each of the five days.
Where to go from here
- Festival calendar every date on this site, with "around" where sources split
- Diwali wishes for each of the five days
- Diwali greetings for clients when you're sending one at work