The reckoning
Panchangam, for your own sky
Five limbs: tithi, vara, nakshatra, yoga, karana. All of it falls out of two things, where the Sun is and where the Moon is, plus the one thing that is yours alone, the patch of horizon you are standing on. This page works it out for your latitude and longitude. Not for your country. Every line will show you its own arithmetic if you ask it to.
When may this be done: pick an act, give the birth stars of the people it is for, and see the next days that hold, with the burnt planets and the extra and empty months already taken out.
Watch a tithi being worked out: the real Sun and the real Moon across one real month, the gap between them opening twelve degrees at a time, and why no two tithis are the same length.
Location and settings tap to change
Nothing is sent anywhere. The whole calculation runs on your phone, which is also why it keeps working with the network off. This panel stays folded away unless you open it, and remembers how you left it.
The day you are reading tap for a calendar
Every box shows the tithi that was running at sunrise that morning here, named in English and in Devanagari. Settings above will drop either one if you would rather have the room. S is the bright half, K the dark. P is Purnima, A is Amavasya, and the eleventh of either half is marked because people look for it. A gold dot means a festival falls on that day at these coordinates, which is not always the same day as somewhere else; a smaller, paler dot is one of the observances that come round every month. The name is cut short to fit, so hold a box to see it whole. Tap a day to read the whole panchangam for it.
Sankalpam the declaration of where and when, for this day open
A rite opens by saying exactly where and exactly when it is being done, from the half of Brahma's life down to the village and the tithi. This asks you for nothing. It takes the place set at the top of the page, works out the land, the river and the town from it, and says under the formula how it got each one. If it has your river wrong, or your tradition says it differently, change it and your wording is kept on this device.
Say it differently
Each box starts with what the page worked out. Type over it and yours is used from then on, here and on your next visit. Empty a box and that line is left out of the formula altogether.
Honest note
This is the common Smarta form and it is not the only one. Sources differ on whether the twenty eighth mahayuga is named, on where the Kali Yuga phrase sits, and on the closing. Vaishnava and several regional forms differ more than that. For a place outside India the dvipa and varsha are genuinely contested: some traditions say Krauncha dvipa and Ramanaka varsha, others keep Jambu and Bharata wherever the person is, and this page will not decide that for you, which is why those boxes start empty off the subcontinent. Where the edge of Bharata runs is a judgement too, not a measurement. The river is picked by distance from a list of courses this page carries, drawn coarsely: it is right about which river, not about which bank, and outside the subcontinent it offers the nearest large river only because that is all geography can tell you. Whether to name the river you live by or the one your family came from is not geography, and not this page's to say. The purpose clause at the end, mamopatta samasta durita kshaya dvara shri parameshvara prityartham, is the general one: for the wearing away of all the wrong I carry, for the pleasure of the Lord. A rite with a purpose of its own puts that purpose here instead, so change that last line to whatever you are actually sitting down to do, and say it the way your own tradition says it.
A day you remember
When does this tithi come round again?
A birthday, a shraddha, the day something happened. Give the date and this reads back the lunar month and the tithi that were running, then works out the next times they return. They do not return on the same date, because a lunar year is about eleven days shorter than a solar one. The day walks backwards through the calendar, then jumps forward by a month when an adhika masa is put in to pull the two back together.
Leave the time blank and it reads the tithi at sunrise, which is the one that owns the day. It uses the place and the clock set above.
What this page is doing, and what it is not
The places of the Sun and Moon come from a modern ephemeris, astronomy-engine, pinned to one exact version. Against the worked examples in Meeus, Astronomical Algorithms, the Moon agrees to 2.3 arcseconds and the Sun to 10.6. At the rate the Moon pulls away from the Sun, that is 21 seconds of clock time on a tithi boundary and 4 seconds on a nakshatra boundary. Which theory supplies the places is the one choice every panchangam maker has always had to make. This one is drik, computed, not vakya.
The panchanga itself is computed here, not looked up. A tithi is twelve degrees of the Moon's lead over the Sun; the page finds the exact instant that lead crosses a multiple of twelve, by bisection, to the second. A nakshatra is one twenty-seventh of the sidereal circle. A yoga is one twenty-seventh of the sum of the two longitudes. A karana is half a tithi.
The ayanamsa is Chitrapaksha by default, the Lahiri value the Indian Calendar Reform Committee settled on in 1955, carried from its value at the start of 2000 by the IAU 2006 precession. It reproduces Lahiri's printed 1900 figure to 15 arcseconds. Four others are in the dropdown. Two of them are anchored to a star rather than to an epoch value: Chitrapaksha done the true way, which is Spica put at exactly 180 degrees tonight and which lands within an arcminute of the Lahiri figure, and Pushya-paksha, which puts Delta Cancri at 16 degrees of Karka after the Surya Siddhanta. That last one runs a degree and eight arcminutes behind Chitrapaksha, which is about two hours on a nakshatra boundary and about a day on a sankranti. Note what the choice does and does not touch: nakshatra, yoga and the rasis move with the ayanamsa, tithi and karana cannot, because the same correction comes off both the Sun and the Moon and the gap between them is unchanged. The solver checks that, across all five, to the millisecond.
Sunrise is the upper limb clearing your own horizon: the centre of the disc at 50 arcminutes below level, which is 34 arcminutes of refraction plus the Sun's own 16 arcminute half-width. That is why the day at the equator on an equinox is twelve hours and seven minutes and not twelve hours flat. Height above sea level dips the horizon further and is yours to set; a panchangam normally takes the sea-level horizon, so it starts at zero.
Daylight saving comes from the IANA time zone database that your browser ships, which is the authority on it. The clock is only ever used for printing. Change the clock and not one computed instant moves. The page also gives you local mean time, four minutes to a degree of longitude, which is the reckoning the classical texts use and which owes nothing to any national meridian.
Honest note. Two things a full panchangam carries are deliberately missing rather than guessed: Durmuhurtam and Amrita ghatika, each of which needs a table this page cannot yet cite. Varjyam is here now, from the tyajya table in the Telugu Muhurta Dipika, scaled to the real length of the nakshatra rather than laid on as wall clock. The names of the thirty muhurtas are left out for the same reason the other two are and they are numbered instead. The eighths of the day are all sourced now. Rahu kalam is page 13 of that book, which gives it as ghadiyas from sunrise and agrees with this page part for part. Yamagandam, Gulika kalam and two more this page did not carry before, Ardhaprahara and Kala, come off page 154, which gives a rule and not a table: the eight parts of the daylight run in weekday order from the day's own lord, and Saturn's part is Gulika, Jupiter's is Yamakantaka, Mercury's is Ardhaprahara and the Sun's is Kala. That rule reproduces the two tables that sat here unverified, row for row, all seven days of both. They are still convention and not astronomy, and the page still says so. Where a tradition differs, this page says so rather than pretending there is one answer. The sampradayam setting is one of those places: it changes the words and nothing else, so the month that the Sanskrit list calls Ashvina is printed Asviyuja for Telugu and Aso for Gujarati, with every instant and every degree untouched. The Tamil, Malayalam and Bengali months are not other names for the lunar month at all: they are the Sun's twelve signs, so those settings print the solar month and say so. The spellings in that list are the ones in common published use as far as this repo can tell, and anyone who reads their own panchangam every year will know better than it does. The Devanagari spellings are the standard ones and are cross-checked against published panchanga lists, but not against a printed panchangam in this repo: if you read the script and one looks wrong, say so. Two of the vasara weekday names, Friday and Saturday, are genuinely disputed between sources and the page prints the dispute rather than choosing. Mrigashira is also printed Mrigashirsha and Mula also Mulam; this page uses one spelling each.
The festival dates that come out of this same engine, and why two cities keep the same festival on different days, are on the festivals page.