Solar Noon Calculator Formula
Understand the math behind the solar noon calculator. Each variable explained with a worked example.
Formulas Used
Offset from Clock Noon
offset_minutes = (standard_meridian - longitude) * 4Solar Noon (decimal hrs)
solar_noon_decimal = 12 + (standard_meridian - longitude) * 4 / 60Variables
| Variable | Description | Default |
|---|---|---|
longitude | Your Longitude(°) | -73.97 |
standard_meridian | Time Zone Meridian(°) | -75 |
How It Works
Solar Noon
Solar noon is when the Sun crosses your local meridian (highest point in the sky). It differs from clock noon because your longitude may not match your time zone's standard meridian.
Formula
Offset = (Standard Meridian - Your Longitude) × 4 minutes
Each degree of longitude corresponds to 4 minutes of solar time (360° / 24 hours = 15°/hour).
The equation of time (up to ±16 min seasonal variation) is not included here.
Worked Example
New York City: longitude -73.97°, Eastern time zone meridian -75°.
- 01Offset = (-75 - (-73.97)) × 4 = -1.03 × 4 = -4.12 min
- 02Solar noon ≈ 12:00 - 4.12 min = 11:55:53
- 03The Sun is highest about 4 minutes before clock noon.
Frequently Asked Questions
Why isn't solar noon at 12:00?
Your location likely is not on the exact standard meridian of your time zone. Also, the equation of time causes seasonal shifts of up to 16 minutes.
What is the equation of time?
A correction for Earth's elliptical orbit and axial tilt, causing solar noon to drift up to 16 minutes early or late through the year. This calculator gives the longitude-based offset only.
Does daylight saving time affect this?
Yes. During DST, clock noon is shifted one hour later, so solar noon is roughly around 1:00 PM clock time.
Ready to run the numbers?
Open Solar Noon Calculator