Solar Noon Time Calculator
Calculate approximate solar noon (local apparent noon) for any longitude and date.
Includes equation of time correction and UTC offset.
Solar noon (local apparent noon) is the moment when the Sun reaches its highest point in the sky for the day. This is when sundials show exactly 12:00.
Simple approximation (no equation of time):
Solar noon (UTC) ≈ 12:00 − longitude / 15
The factor 15 comes from Earth rotating 360° in 24 hours → 15° per hour.
The Equation of Time (EoT): Due to Earth’s elliptical orbit and axial tilt, solar noon can differ from clock noon by up to ±16 minutes. This difference is called the Equation of Time.
Approximate EoT formula:
EoT ≈ 9.87 sin(2B) - 7.53 cos(B) - 1.5 sin(B) (minutes)
Where B = 360/365 × (day_of_year - 81) degrees.
The analemma: If you photographed the Sun at the same clock time each day for a year, it would trace a figure-8 pattern in the sky called the analemma. The horizontal position shows the Equation of Time; the vertical position shows the Sun’s declination.
Longitude convention:
- Positive (+) = East of Greenwich (Europe, Asia, Africa, Australia)
- Negative (−) = West of Greenwich (Americas)
Practical note: Legal (civil) noon is determined by time zones, which are fixed 15° bands (in theory). Real time zones follow country and state borders, so they can differ significantly from true solar noon. For example, western China and far western Spain both use UTC+8 and UTC+1 respectively, so solar noon there can be 2–3 hours away from clock noon.