Sunrise & Sunset Calculator
Calculate sunrise, sunset, and solar noon times for any location and date. Choose from presets for all 47 Japanese prefectural capitals, or enter latitude and longitude directly. Useful for planning photography, fishing, and hiking. All calculations run in your browser, so the location and date you enter are never sent anywhere.
The location and date you enter are processed entirely in your browser and are never sent anywhere.
Enter a location and date, then press "Calculate".
- Sunrise
- Sunset
- Solar noon
- Day length
How to use
- Choose a city from the 47 Japanese prefectural capitals, or switch to "Enter latitude / longitude" for any location.
- Pick a date (today by default).
- Press "Calculate" to see sunrise, sunset, solar noon, and day length.
How it works
How it works
This tool uses the "General Solar Position Calculations" formulas published by the NOAA Global Monitoring Division. These are a simplified version based on Jean Meeus's book Astronomical Algorithms, and are the same family of formulas used by the official NOAA Solar Calculator.
From the latitude, longitude, and date, the tool computes the sun's declination and the equation of time, then solves for the hour angle at which the sun's center is 0.833 degrees below the horizon (accounting for atmospheric refraction and the sun's apparent size) to derive sunrise and sunset. Everything runs as pure computation inside your browser; no server is contacted.
Accuracy
This simplified formula omits higher-order corrections such as nutation, so results can differ from high-precision ephemeris data (such as Japan's National Astronomical Observatory almanac) by roughly 1-2 minutes. This implementation was checked against published National Astronomical Observatory of Japan (NAOJ) sunrise/sunset times for Tokyo and Naha (multiple dates in 2026), and all results were within 2 minutes of the official figures. This is more than sufficient accuracy for everyday planning such as photography, fishing, or hiking. If you need astronomically exact times, consult a primary source such as NAOJ's official almanac.
About timezones
When you choose one of the Japanese city presets, the calculation is fixed to Japan Standard Time (UTC+9, no daylight saving). When you enter latitude/longitude directly, you must also enter that location's timezone offset from UTC yourself.
Midnight sun and polar night
At high latitudes near the Arctic or Antarctic Circle, the sun may not set for an entire day (midnight sun) or not rise at all (polar night) depending on the season. In these cases sunrise and sunset cannot be defined, so the tool reports this instead (solar noon can still be calculated even during midnight sun or polar night).
FAQ
Is the location or date I enter sent to a server?
No. All calculations happen entirely inside your browser. The formulas and the list of Japanese city coordinates are bundled with the page, so no network requests are made after the page loads.
How accurate are the times shown?
This tool uses NOAA's published simplified solar calculation formulas, which can differ from high-precision ephemeris data by roughly 1-2 minutes. We verified the implementation against official National Astronomical Observatory of Japan sunrise/sunset times for Tokyo and Naha, and all results were within 2 minutes. That is more than accurate enough for everyday use.
Can I calculate times for locations outside Japan?
Yes. Switch to "Enter latitude / longitude", then enter the location's coordinates and its timezone offset from UTC. The city presets only cover Japan's prefectural capitals, but any location worldwide can be calculated if you know its latitude and longitude.
Why does it show "midnight sun" or "polar night"?
At latitudes close to the Arctic or Antarctic Circle, the sun can stay above the horizon all day (midnight sun) or below it all day (polar night) depending on the season. In that case sunrise and sunset don't exist as concepts, so the tool reports this state instead of a time.
How is day length calculated?
It is the number of minutes between sunrise and sunset. On days with midnight sun or polar night, sunrise and sunset are undefined, so day length cannot be calculated either.
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