Festivals
The Indian festival calendar — how the dates are worked out
Before the list of dates, the thing the lists never explain — why there is no single correct date for most Indian festivals.
The short answer
Indian festivals are set by a lunisolar calendar, so their Gregorian dates move each year. A festival falls on a lunar day, a tithi, which begins and ends at a clock time that differs by longitude — which is why a date computed for Chennai can be a day off for New Jersey.
Key facts
- The calendar
- Lunisolar — months follow the moon, years are kept aligned to the sun by an intercalary month, adhika māsa, roughly every 32 to 33 months
- The unit that matters
- The tithi, a lunar day, defined by the angle between sun and moon — so it is not 24 hours long and does not start at midnight
- Two month systems
- Amānta, months ending at the new moon, used in the south and west; Pūrṇimānta, ending at the full moon, used in much of the north
- Regional solar calendars
- Tamil, Malayalam (Kollavarsham), Bengali and Assamese calendars run on solar reckoning and set their own new year
- What a date needs
- A location and a panchang tradition. A festival date given without either is incomplete
The short version
Most Indian festivals are set by the moon, and the moon does not keep step with the Gregorian calendar. A festival that falls in early November one year falls in late October the next, drifts back, and then jumps forward when an extra month is inserted to stop the seasons sliding.
That is why the date changes. What follows is why two calendars can disagree even in the same year.
The tithi is not a day
The lunar day, the tithi, is defined by the angle between the sun and the moon — each tithi is the time the moon takes to gain twelve degrees on the sun. That takes anywhere from about nineteen to about twenty-six hours, and it begins whenever it begins, not at midnight.
So a tithi can start at four in the afternoon on Tuesday and end at one in the afternoon on Wednesday. Which of those two days "is" the festival depends on rules — usually about which day the tithi is current at sunrise, or at midnight, or at the specific hour the observance requires.
Two consequences follow, and between them they explain nearly every calendar disagreement:
- Location changes the answer. Sunrise in Chennai and sunrise in New Jersey are hours apart, so the tithi at sunrise can fall on different Gregorian days.
- Tradition changes the answer. Where an observance depends on a particular hour — midnight for Janmashtami, the fourth watch of the night for Shivaratri — different traditions apply different rules when the tithi does not cover that hour cleanly.
The two month systems
Both are correct, and both are in daily use.
| System | Month ends at | Used in |
|---|---|---|
| Amānta | New moon | Gujarat, Maharashtra, Karnataka, Andhra, Telangana, Tamil Nadu, Kerala |
| Pūrṇimānta | Full moon | Most of North and Central India |
The festivals fall on the same nights in both. Only the month names attached to them differ, which is why the same festival is described as belonging to different months in different books.
The solar calendars
Several regions run solar calendars alongside the lunar one, and these set the regional new year:
- Tamil Nadu — Puthandu, at the sun's entry into Mesha
- Kerala — Vishu, on the same solar event, with the Kollavarsham year counted separately
- Bengal and Assam — Poila Boishakh and Bohag Bihu, in the same mid-April window
- Punjab — Vaisakhi, likewise, and a harvest festival as well as a calendar marker
This is why mid-April carries a cluster of new years across otherwise unrelated regions: they are all keyed to the same solar moment.
How to find a date you can trust
- Use a computation made for your location, not for India, if you live elsewhere. Several established panchang services publish city-specific dates.
- Check what your temple or your family follows, particularly for Janmashtami and Shivaratri, where traditions genuinely diverge and both dates are legitimate.
- For anything with a muhurta — Holika Dahan, Ghatasthapana, Lakshmi Puja — the hour matters as much as the day, and only a panchang gives you the window.
- Expect two dates in some years. It is not an error, and picking the one your household has always followed is the correct resolution.
Questions people ask
Why does my phone calendar disagree with the temple's calendar?
Usually because they were computed for different places, or because they follow different rules for which day a tithi belongs to when it spans midnight. Both may be correctly computed. For an observance kept at a specific hour — Janmashtami at midnight, Shivaratri through the night — the difference matters and is worth resolving with your own temple.
What is an adhika masa?
An extra month inserted to keep the lunar year in step with the solar one, roughly every 32 to 33 months. In a year that has one, festivals in the affected months shift, and some observances are kept in the intercalary month and some are not — which is a question for a panchang rather than a rule of thumb.
Why do the north and south call the same month by different names?
They divide the month at different points. Under the Amānta system used in the south and west, a month ends at the new moon; under Pūrṇimānta in the north, it ends at the full moon. The same night can therefore sit in Ashvina in one system and Kartika in the other, which is why Diwali is described as a Kartika festival in some places and an Ashvina one in others.
Which panchang should I follow?
The one your family or your temple follows. There are several established traditions of computation, and they occasionally differ by a day. Consistency within a household matters more than picking a notionally superior one.
Sources (3)
- Indian Calendric System, Government of India publications on the reformed national calendar — For the structure of the lunisolar calendar and the 1957 reform
- Printed panchang traditions — Vishvavijaya, Kalnirnay, Vakya and Drik systems — For the differences in computation that produce differing dates
- Robert Sewell and Sankara Balkrishna Dikshit, The Indian Calendar — For the historical reckoning and the intercalary month
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