Solar Noon Calculator
Find the exact instant of Local Apparent Noon (when the sun crosses the meridian and reaches highest elevation). Official NOAA solar calculation algorithm with Equation of Time analysis.
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What is Local Apparent Noon (Solar Noon)?
Solar noon is the moment when the Sun culminates — crossing the celestial meridian to attain its highest angular position in the sky for that date at your specific longitude. It is the astronomical midpoint between true sunrise and sunset.
Why Solar Noon is Not 12:00 PM
Most people expect solar noon to occur at 12:00:00 on the clock, but it almost never does. Three independent factors shift the time of solar noon:
- Longitude within Time Zone: Standard time zones are 15 degrees wide. For every 1 degree of longitude you are located east or west of your time zone's center meridian, solar noon shifts by exactly 4 minutes.
- Daylight Saving Time (DST): During summer DST periods, clocks are moved forward 1 hour, making solar noon typically occur near 1:00 PM local time.
- The Equation of Time (EoT): The Earth's orbit is slightly eccentric (elliptical) and tilted by 23.44 degrees relative to the celestial equator. As the Earth moves faster at perihelion (January) and slower at aphelion (July), true solar days vary by up to ±16.4 minutes from a uniform 24-hour clock.
NOAA Solar Calculation Formulation
This calculator computes solar transit using the official NOAA Solar Calculator algorithm:
Solar Noon (minutes UTC) = 720 − 4 × Longitude − Equation_of_Time
The solar altitude angle is calculated as:
Altitude = 90° − Latitude + Solar_Declination
Frequently Asked Questions
What is solar noon?
Solar noon (also called local apparent noon or meridian transit) is the exact moment the sun crosses your celestial meridian and reaches its highest point (maximum elevation angle) in the sky for the day. At solar noon, a vertical stick or gnomon casts its shortest shadow, pointing directly true north (in the Northern Hemisphere) or true south (in the Southern Hemisphere).
Why is solar noon rarely at 12:00 PM on a clock?
Clock time is standardized across entire 15-degree wide time zones for human convenience. In reality, the sun crosses the meridian at slightly different clock times depending on: 1) your exact longitude relative to your time zone's reference meridian (each degree of longitude shifts solar noon by 4 minutes), 2) Daylight Saving Time (+1 hour offset in summer), and 3) the Earth's elliptical orbit and axial tilt (the Equation of Time, which shifts solar noon by up to ±16 minutes throughout the year).
How does the NOAA solar algorithm calculate solar noon?
This calculator implements the official National Oceanic and Atmospheric Administration (NOAA) solar positioning equations. It computes the Julian Day, solar mean anomaly, ecliptic coordinates, and the Equation of Time (EoT), then solves for the transit instant: Solar Noon = 720 − 4 × Longitude − Equation of Time (in minutes UTC). The result is converted to your exact local clock time with ±1 minute astronomical accuracy.
What is solar altitude and solar declination?
Solar altitude is the angle of the sun above the horizon in degrees (0° at the horizon, up to 90° directly overhead at the zenith). Solar declination is the angle between the Earth's equator and the rays of the sun, oscillating between +23.44° (June solstice) and -23.44° (December solstice). At solar noon, your maximum solar altitude equals 90° − Latitude + Declination.
How do solar panel installers and sailors use solar noon?
Solar panel designers use solar noon and peak solar altitude to calculate optimal tilt angles and seasonal orientation for photovoltaic arrays. Celestial navigators use local apparent noon to measure their exact latitude with a marine sextant (sight reduction).