Why a muhūrtham changes between India and California

One sky, many sunrises

The Moon is where it is. At any single instant, the angle between the Moon and the Sun is one number for everybody on Earth, so the tithi running at that instant is the same in Madurai and in Milpitas.

But an almanac does not report instants; it reports days. And a day is named for the tithi running at its sunrise. Sunrise in the Bay Area happens about thirteen and a half hours after sunrise in Tamil Nadu. In that gap, a tithi can end and the next begin. The two almanacs then name the day differently — and both are right about their own place.

The restricted periods move too

Rāhu Kālam is not a fixed clock time. It is one eighth of the day between sunrise and sunset, assigned by weekday. In midsummer in the Bay Area that eighth is about ninety-four minutes long; at midwinter it is about seventy. A table of Rāhu Kālam times printed for Chennai is simply not about here.

The same is true of Durmuhūrtam, of Abhijit, and of Brahma Muhūrta, all of which are fractions of the local day or the local night.

Which is why this site computes rather than copies

It would be far easier to reprint an Indian almanac. It would also be wrong for the families this site is for, and it would be someone else’s work.

Everything here is computed from the Sun’s and the Moon’s positions for the coordinates and timezone you choose, with daylight saving handled by name rather than by a fixed offset — so the answer stays right through the March and November transitions without anybody editing anything.

What a family may do

• When family in India name a date, treat it as the tithi rather than as the date, and check what that tithi does here.
• For a ceremony at a venue outside your own city, use that venue’s location. A few minutes of sunrise difference rarely matters; a few hundred miles can.
• If two sources disagree by a whole day, the reason is nearly always this one.

Often misunderstood

• That the tithi itself differs between countries. It does not — only which one holds at sunrise.
• That an Indian almanac is “more authentic” for a ceremony held here. It is authentic about India.

Where traditions differ

• Where a family keeps a festival on the date observed at their home temple in India rather than the locally computed one, that is a considered choice and not an error. It is worth deciding deliberately, and worth telling the priest.

Explaining it to a child

The Sun rises here much later than it does in India — while they are having lunch, we are still asleep. The Moon does not wait for us, so by the time our day starts, the lunar day may already have changed.