A festival is observed on the day a particular tithi (lunar day) is current at a particular local moment -- usually sunrise, sometimes sunset, midnight or moonrise. The tithi itself begins and ends at one instant for the whole world, but that instant falls on a different local clock time in each country. In the Americas, roughly nine to thirteen and a half hours behind India, it can already be current at a sunrise that is still the previous calendar day in India -- so the observance lands a day earlier. East of India, in Australia or New Zealand, it can land a day later. Neither date is wrong; each is correct for where it is kept.
☕ One moment, many clocks
A tithi is a stretch of the Moon's journey away from the Sun: every 12 degrees of separation is one tithi. When the Moon crosses the next 12-degree mark, the tithi changes -- and that happens at the same instant whether you are in Chennai, Chicago or Sydney. What differs is what your wall clock says at that instant.
Most vratas and festivals are fixed by asking a simple question: which tithi is current at sunrise here? Ekadashi, most annual festivals and the monthly calendar all use a local moment. Pradosham looks at the local twilight, Krishna Janmashtami at local midnight, Karwa Chauth and Sankashti at local moonrise.
So two things change when you move: the clock time of the tithi's beginning and end, and the moment of your own sunrise. Change either enough and the answer to which tithi is current at my sunrise? moves to the neighbouring day.
This is why a family in New Jersey can keep Ekadashi on a Tuesday while their parents in Madurai keep it on Wednesday -- and why a panchangam printed for India is the wrong calendar to hang in a kitchen in Houston.
What moves, and what does not
- The instant a tithi or nakshatra begins and ends is the same everywhere; only the clock time you read it in changes
- Your local sunrise decides the day for most vratas, so follow a panchangam computed for your own city
- In the Americas an observance can fall a day EARLIER than in India; in Australia and New Zealand, a day LATER
- Daylight-saving changes move the clock time by an hour, never the tithi -- a correct panchangam applies them for you
- Assuming India's date is the 'real' one and yours is an error -- each is correct for the place it is kept
- Converting an Indian panchangam's end time to your clock and stopping there: you must also ask what was current at YOUR sunrise
- Treating a family or temple that deliberately keeps India's date as wrong -- that is a choice of practice, not a calculation
- Using a fixed UTC offset all year in a country that changes its clocks for summer
Frequently asked questions
Why is Ekadashi a day earlier in the USA than in India?
Because Ekadashi is kept on the day its tithi is current at local sunrise. The USA is about nine to thirteen and a half hours behind India, so the moment Ekadashi begins can fall before a US sunrise that is still the previous calendar day in India. The observance then lands a day earlier in the USA.
Can a festival be a day later outside India?
Yes. East of India -- Australia, New Zealand, and sometimes Singapore and Malaysia by a smaller margin -- local clocks run ahead of Indian time, so a tithi that is current at an Indian sunrise may begin after the local sunrise that day and be observed the next day instead.
Should I follow the Indian date or my local date?
The classical rules are written in terms of your own sunrise, sunset and midnight, which is why a panchangam computed for your city gives your local date. Some families and temples abroad deliberately keep India's date; that is a matter of practice, and your family priest or temple is the right person to ask.
Is the tithi end time different in each country?
The moment is the same everywhere; the clock time is not. A tithi ending at 9:30 PM in India ends at noon in New York during daylight saving time -- the same instant, read on a different clock.
Does Nava Panchangam give the correct date for my city abroad?
Nava computes sunrise, sunset and every window derived from them for the coordinates of 14,654 cities, 10,438 of them outside India, and applies each city's own timezone and daylight-saving rules. Under the Vakya system, tithi and nakshatra ending instants follow the almanac's own single reckoning, as printed almanacs do; your local sunrise then decides which day they fall on.
Deep dive: a worked example
Illustrative round times, chosen so the arithmetic is easy to follow. They describe no particular date.
🌍 The same Ekadashi in Chennai and New York
Suppose Ekadashi begins at 3:00 PM on a Tuesday, India time, and lasts about a day, ending around 4:00 PM on Wednesday. New York is 9 hours 30 minutes behind India during daylight saving time.
Chennai: Wednesday sunrise (~6:00 AM) → Ekadashi current → kept on Wednesday
New York: begins 5:30 AM Tuesday local time
New York: Tuesday sunrise (~6:30 AM) → Ekadashi already current → kept on Tuesday
Nothing about the Moon changed. The same instant simply fell before New York's Tuesday sunrise and after Chennai's.
🌅 Why east of India can be a day later
Now suppose a tithi begins at 3:00 AM on a Tuesday, India time. Sydney is 4 hours 30 minutes ahead of India in the southern winter.
Sydney: begins 7:30 AM Tuesday local time → after Sydney's sunrise (~6:45 AM) → kept on Wednesday
If the tithi ends before Wednesday's sunrise in Sydney, the calendar has a gap to resolve (a kshaya tithi); each tradition's rules say which day then carries the observance.