Why this sunrise differs from the one in the newspaper

Two things move a printed sunrise away from the one computed for your own doorstep. The first is a definition: almanacs do not agree on which part of the Sun has to be above the horizon before the Sun counts as risen. The second is geography: a newspaper prints one time for a whole edition area, while sunrise moves about four minutes for every degree of longitude. Between them they account for most disagreements of five to twenty minutes.

Neither is an error. They are two conventions and one simplification. This site computes sunrise for the town you name, under the convention you choose, and says which one it used.

The default here is the first gleam of the Sun’s upper edge over a level horizon. At that moment the Sun’s centre is still about 50 arc-minutes below the true horizon: 16 for its own half-width and 34 for the bending of light through the air. That is the convention of Meeus, the Nautical Almanac and the Indian Astronomical Ephemeris, and it is the sunrise the Rashtriya Panchang and most modern almanacs print.

The Surya Siddhanta takes something else: the centre of the Sun’s disc on the true, airless horizon, seen from the centre of the Earth. Some Tamil almanacs still print that sunrise. It is later, because the Sun has to climb further before it counts.

The gap is small and it is not nothing. At Chennai this engine puts the siddhantic sunrise 3.4 minutes after the default one at the March equinox and 3.8 minutes after it at the December solstice, with sunset coming as much earlier. The siddhantic day is therefore about seven minutes shorter at both ends, and everything measured as a fraction of the daylight shifts with it.

Both are offered on the Settings page, along with the two mixed cases, the upper edge without refraction and the centre with it. The app does not hold that one of them is the real sunrise. It holds that a page should name the one it used.

The Earth turns 360 degrees in 24 hours, so one degree of longitude is four minutes of time. The towns in this app’s Tamil Nadu list run from 76.7°E at Udhagamandalam to 80.3°E on the Chennai coast. That is three and a half degrees, or about a quarter of an hour, inside one state.

The numbers are not theoretical. On 21 March 2026 this engine puts sunrise at Chennai at 06:13 and at Coimbatore at 06:26. On 21 June it is 05:44 at Chennai and 06:01 at Coimbatore: seventeen minutes apart on the same morning. A single printed time can only be right for one meridian, and it is usually the one the press sits on.

Longitude does most of that, and latitude adds the rest away from the equinoxes. At the March equinox the Chennai to Coimbatore gap is the thirteen minutes their longitudes alone demand. In June the more northerly Chennai gains a few minutes on top, because its day is longer.

This is the correction to make first. Entering your own town rather than the state capital removes most of the disagreement before any question of convention arises.

Sunrise is not one line on the page. It is the origin every other reading on a panchangam is measured from, so a sunrise that is ten minutes out carries a great deal with it.

The day’s tithi, nakshatra, yoga and karana are the ones running at sunrise. A tithi that ends at 06:20 belongs to today under one sunrise and to yesterday under another, and the whole day’s panchangam turns over with it.

Rahu kaal, Yamaganda, Gulika and the Gowri parts are eighths of the daylight from sunrise to sunset, so both ends move them. Abhijit is the eighth of fifteen muhurtas cut from the same daylight. Nalla neram is picked out of those parts. The muhurtham search walks the rising sign through the daylight and then cuts those windows out of it.

Most festival dates are settled by which tithi is running at a named instant, and every one of those instants is counted from sunrise or sunset. Arunodaya is the 96 minutes before sunrise. Aparahna runs from six tenths to eight tenths of the daylight after it. Pradosha runs from sunset to about 2 hours 24 minutes after it, and nishita is the midpoint of the night. The Tamil month itself begins on the ingress day only when the ingress came before local sunset.

Measured against the Swiss Ephemeris on the same convention, the rise and set times here are within 1.7 seconds. What remains is the refraction constant rather than an error: 34 arc-minutes is the conventional horizontal refraction of the almanacs, while the Swiss library computes refraction for a stated pressure and temperature and lands a couple of seconds away.

Where the Sun neither rises nor sets, far enough north or south, the app says so rather than inventing a time.

If the almanac your family keeps prints the siddhantic sunrise, set it on the Settings page and the whole site follows: the panchangam, the Tamil and regional calendars, the muhurtham windows, Rahu kaal and the other day windows, and the chart values that start from sunrise. If it prints the modern one, leave the default alone.

Then set your own place. Between the convention and the meridian, those two settings are usually the whole of the difference, and once they match your almanac the rest of the page will match it too.

The five limbs of a day, with the good and bad hours.

Panchangam →