How it works
- Longitude: each US time zone keeps the clock of a standard meridian (75°W Eastern, 90°W Central, 105°W Mountain, 120°W Pacific, 135°W Alaska, 150°W Hawaii). The Sun crosses 1° every 4 minutes, so a city 8° west of its meridian sees noon 32 minutes late. Daylight saving time adds 60 minutes.
- Equation of time: Earth's elliptical orbit and tilted axis make the real Sun run ahead of or behind the average Sun, from about −14 minutes (mid-February, noon is later) to +16 minutes (early November, noon is earlier).
- Noon Sun height = 90° − |latitude − solar declination|. Declination is 0° at the equinoxes and about ±23.4° at the solstices. Refraction is left out; the height is for the Sun's center.
- Earth's spin = Earth's rotation rate (7.292115 × 10⁻⁵ rad/s) × your distance from the spin axis, using the WGS 84 ellipsoid. The equator moves about 1,040 mph (1,674 km/h); the speed drops toward the poles. Earth's orbital speed around the Sun (18.5 miles per second) is not included.
- The equation of time and declination use the formulas in NOAA's Solar Calculator (based on Jean Meeus, Astronomical Algorithms) and match Meeus's worked examples (October 13, 1992: equation of time 13.709 min, declination −7.785°).
City offsets and noon Sun height at the solstices
| City | Standard time | Daylight time | Equinox | June | December |
|---|---|---|---|---|---|
| New York | 4 min earlier | 56 min later | 49.3° | 72.7° | 25.9° |
| Boston | 16 min earlier | 44 min later | 47.6° | 71.1° | 24.2° |
| Detroit | 32 min later | 92 min later | 47.7° | 71.1° | 24.2° |
| Chicago | 9 min earlier | 51 min later | 48.1° | 71.6° | 24.7° |
| Houston | 21 min later | 81 min later | 60.2° | 83.7° | 36.8° |
| Denver | on time | 60 min later | 50.3° | 73.7° | 26.8° |
| Phoenix | 28 min later | no DST | 56.5° | 80.0° | 33.1° |
| Los Angeles | 7 min earlier | 53 min later | 56.0° | 79.4° | 32.5° |
| Seattle | 9 min later | 69 min later | 42.4° | 65.8° | 19.0° |
| Anchorage | 60 min later | 120 min later | 28.8° | 52.2° | 5.3° |
| Honolulu | 31 min later | no DST | 68.7° | 87.9° | 45.3° |
The offset from longitude never changes; add the day's equation of time to get solar noon. Solstice heights use declination 0° and ±23.437° (Earth tilt around 2026), so they move by about 0.01° from year to year. City coordinates are city-hall locations rounded to two decimals.
Frequently asked questions
Why isn't solar noon at 12 PM?
Clocks follow the standard meridian of each time zone: 75°W for Eastern, 90°W for Central, 105°W for Mountain, 120°W for Pacific. The Sun crosses 1° of longitude every 4 minutes, so a city west of its meridian sees noon later. Daylight saving time adds another hour: in Detroit (83°W), solar noon on July 15, 2026 is about 1:38 PM EDT.
When is solar noon in New York?
About 12:42 PM EDT on October 12, 2026, and about 11:54 AM EST on December 21, 2026. It shifts through the year by up to about half an hour because of the equation of time.
How high does the Sun get at noon?
Noon altitude = 90° − latitude + the Sun's declination. Declination is 0° at the equinoxes, about +23.4° at the June solstice and about −23.4° at the December solstice, so in New York (40.7°N) the noon Sun reaches about 49.3° at the equinoxes, 72.7° in late June and 25.9° in late December.
What is the equation of time?
It's the gap between sundial time (the real Sun) and clock time (an averaged Sun). Earth's elliptical orbit and 23.4° axial tilt make the real Sun run up to about 16 minutes early in early November and about 14 minutes late in mid-February.
How accurate is this?
It uses NOAA's solar calculator formulas, which NOAA says are good to within a minute between 72°N and 72°S. Times are shown to the minute. Noon altitude is for the Sun's center without atmospheric refraction.
How fast is New York moving as Earth spins?
Earth turns once about every 23 hours 56 minutes. The equator moves about 1,040 mph (1,674 km/h), and the speed drops as you go toward the poles because you are closer to the spin axis. New York (40.71°N) moves about 790 mph (1,271 km/h). The figure uses the WGS 84 ellipsoid and a rotation rate of 7.292115 × 10⁻⁵ rad/s.