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Omnikalc

Solar noon and equation of time calculator

Find the clock time of solar noon for any date and place, the equation of time that shifts it through the year, and the sun's height at noon.

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Solar noon (clock time)

11:40 AM

Sun's height above the horizon at solar noon

33.1 °

Equation of time (sundial ahead of mean time when positive)
16.3 min
Longitude correction from the time zone meridian
-4.0 min
Daylight saving time applied
0
No: standard time
Solar declination
-16.18 °

What solar noon is

Solar noon is the moment the sun crosses your local meridian and reaches its highest point of the day. Shadows point due north (in the Northern Hemisphere) and are at their shortest. It almost never happens at 12:00 on the clock, for three reasons.

  1. Longitude. A time zone is 15° wide and its clocks follow one central meridian (75° W for US Eastern time, 15° E for Central European time). Every degree you sit west of that meridian makes solar noon 4 minutes later.
  2. Daylight saving time. Clocks move one hour ahead in summer, so solar noon moves an hour later on the clock.
  3. The equation of time. Earth’s tilted axis and elliptical orbit make the sun run up to 16 minutes ahead of, or 14 minutes behind, an even clock over the year.

The formula

Solar noon (minutes after midnight) = 720 − 4 × longitude − equation of time + 60 × UTC offset (+ 60 if DST)

Longitude is positive east. The calculator uses a standard approximation of the equation of time:

B = 360 × (day of year − 81) ÷ 365 EoT ≈ 9.87 sin 2B − 7.53 cos B − 1.5 sin B (minutes)

It is accurate to about a minute, which is plenty for photography, sundials or gardening.

Example

New York sits at 74.0° W, very close to the 75° W Eastern meridian, so the longitude correction is only about −4 minutes. On November 4 the equation of time is about +16 minutes (sundials run fast), and DST has just ended. Solar noon falls near 11:40 AM. In mid-July, with DST and an equation of time of about −6 minutes, it is close to 1:02 PM.

Automatic daylight saving time

  • US rules: from the second Sunday of March to the first Sunday of November.
  • EU rules: from the last Sunday of March to the last Sunday of October.

Choose “Always on” or “Never” if your area does not follow these rules, such as Arizona or Hawaii.

Sun height at noon

The calculator also estimates the sun’s noon elevation: 90° − |latitude − solar declination|. The declination swings between +23.44° at the June solstice and −23.44° at the December solstice. A negative value means the sun does not rise at all that day.

Uses

  • Setting up a sundial or checking one.
  • Planning photos with the shortest shadows or harsh overhead light.
  • Finding true north: at solar noon a vertical stick’s shadow points along the meridian.

Frequently asked questions

Why isn't solar noon at 12:00?

Your longitude is rarely on your time zone's central meridian, daylight saving time adds an hour, and the equation of time shifts the sun by up to about 16 minutes through the year.

What is the equation of time?

It is the difference between sundial time and clock time, caused by Earth's tilted axis and elliptical orbit. It peaks near +16 minutes in early November and about −14 minutes in mid-February.

Does latitude change solar noon?

No. Solar noon depends only on longitude, time zone and date. Latitude changes how high the sun gets at noon, which the calculator also shows.

Is solar noon halfway between sunrise and sunset?

Very nearly. Small effects such as refraction make the two halves differ by a few seconds, so it is a good way to check a sunrise and sunset table.

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Results are estimates provided for information purposes. They do not replace professional advice.

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