Guide
Why Do Diwali, Holi and Other Hindu Festivals Fall on Different Dates Every Year?
Diwali, Karwa Chauth, Navratri and most other Hindu festivals fall on a different Gregorian calendar date every year, not because of inconsistency, but because they follow a lunar calendar (the tithi system) rather than the fixed solar calendar most of the world uses day to day.
Tithi, not date, is what's actually fixed
A festival like Diwali is defined by a specific tithi (lunar day) in a specific lunar month, Amavasya (new moon) of Kartik, for Diwali, not by a Gregorian calendar date. Because a lunar month (about 29.5 days) doesn't divide evenly into a solar year (365.25 days), that fixed tithi lands on a different Gregorian date each year, shifting by roughly 10-11 days annually before periodically correcting.
Why some years get an extra "leap" month
To keep the lunar calendar roughly aligned with the seasons over time, an extra intercalary month (Adhik Maas) is inserted periodically, which is also why the yearly drift doesn't just accumulate indefinitely and festivals stay within a predictable few-week range rather than migrating through the entire year the way, for comparison, the Islamic calendar does.
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Why the exact time (not just date) matters too
Because a tithi begins and ends at a specific moment, not midnight to midnight, the same festival can technically be observed a day earlier or later depending on where the tithi falls relative to sunrise in a specific city, which is why festival times are calculated per location, not just once for a single date nationwide.
What this means for planning ahead
A specific city's exact puja time, moonrise time or muhurat for a festival can only be calculated accurately once the tithi and astronomical data for that year are available, which is why dates for festivals more than a couple of years out are typically approximate until closer to the time.
Frequently asked questions
Why does Diwali fall on a different date every year?
Diwali is fixed to a specific lunar tithi (Amavasya of Kartik), not a Gregorian date, and lunar months don't divide evenly into a solar year, so the Gregorian date shifts annually.
What is Adhik Maas?
An extra lunar month inserted periodically to keep the lunar calendar roughly aligned with the solar year and seasons, preventing festival dates from drifting indefinitely.
Why do festival times differ by city?
A tithi begins and ends at a specific moment, and its relationship to sunrise/sunset differs by location, so puja times and moonrise-based festivals are calculated per city.
Astrology, tarot, numerology and related practices are offered for reflection and entertainment and are not medical, legal or financial advice.