Astronomy Day Length Calculator
Calculate sunrise, sunset, solar noon, and day length for any date and location using the NOAA solar position algorithm. Enter your coordinates and date to get precise sunrise and sunset times, day length, night length, and maximum solar elevation — with automatic polar day and polar night detection. All calculations run locally in your browser with no signup required.
Calculate sunrise, sunset, solar noon, and day length for any date and location using the NOAA solar position algorithm. Accurate to within 1 minute for most locations. All calculations run locally in your browser with no signup required.
Quick Locations
Why Use Our Astronomy Day Length Calculator?
Accurate, private, and fully browser-based sunrise and sunset calculation
Instant Sunrise & Sunset Calculation
Calculate sunrise, sunset, solar noon, day length, night length, and maximum solar elevation instantly for any date and location. The astronomy day length calculator uses the NOAA solar position algorithm — accurate to within 1 minute for most locations.
Secure Day Length Calculator Online
The astronomy day length calculator runs entirely in your browser. Your location coordinates, dates, and calculation results never leave your device — no server, no account, no tracking. Your data stays completely private.
Day Length Calculator - No Installation
Use the astronomy day length calculator directly in any modern browser with no downloads, apps, or plugins required. Supports polar day (midnight sun) and polar night detection for high-latitude locations.
100% Free for Any Date and Location
The astronomy day length calculator is completely free with no signup, no usage limits, and no ads. Calculate sunrise and sunset for any date — past, present, or future — and any location on Earth, completely free forever.
Common Use Cases for Astronomy Day Length Calculator
Practical applications of sunrise, sunset, and day length calculations
Photography and Golden Hour Planning
Photographers use the astronomy day length calculator to plan shoots around golden hour — the period just after sunrise and before sunset when light is warm and directional. Enter your shoot date and location to find the exact sunrise and sunset times.
Gardening and Agriculture
Gardeners and farmers use the day length calculator to track photoperiod — the number of daylight hours that trigger flowering and fruiting in plants. Calculate day length for any date to plan planting and harvesting schedules.
Travel and Itinerary Planning
Travellers use the astronomy day length calculator to understand how much daylight they'll have at their destination. Calculate sunrise and sunset for your travel dates to plan outdoor activities and avoid being caught in the dark.
Solar Energy and Panel Positioning
Solar installers and homeowners use the day length calculator to estimate daily solar energy production potential. The maximum solar elevation angle helps determine optimal panel tilt angles for different seasons.
Polar Region Research
Researchers and travellers visiting high-latitude locations use the astronomy day length calculator to check for midnight sun and polar night conditions. The calculator detects and clearly labels these special cases for any Arctic or Antarctic location.
Religious and Cultural Observances
Many religious observances are tied to sunrise and sunset times — prayer times, Shabbat, Ramadan fasting, and more. Use the astronomy day length calculator to find precise sunrise and sunset times for any date and location worldwide.
Understanding the Astronomy Day Length Calculator
How sunrise and sunset are calculated and what the results mean
What is Day Length?
Day length (also called photoperiod) is the number of hours between sunrise and sunset on a given day at a specific location. It varies throughout the year because Earth's axis is tilted at approximately 23.5° relative to its orbital plane — this tilt causes the seasons and the changing length of days. At the summer solstice (around June 21 in the Northern Hemisphere), day length is at its maximum; at the winter solstice (around December 21), it is at its minimum. At the equinoxes (around March 20 and September 22), day and night are approximately equal at 12 hours each. Our astronomy day length calculatoruses the NOAA solar position algorithm based on Jean Meeus's Astronomical Algorithms to calculate sunrise, sunset, solar noon, and day length accurately for any date and location.
How Our Astronomy Day Length Calculator Works
- Enter Your Location and Date:Enter the latitude and longitude of your location (or click a preset city), the date you want to calculate for, and your UTC offset for local time display. You can also click "Use my current location" to auto-fill your coordinates using the browser's geolocation API.
- Instant Browser-Based Calculation: Click Calculate and the astronomy day length calculator computes the Julian Day Number, solar declination, equation of time, and hour angle using the NOAA algorithm. All calculations run locally in your browser — your location data never leaves your device.
- Read Your Results: The calculator shows sunrise, sunset, solar noon, day length, night length, and maximum solar elevation. A visual day/night bar shows the proportion of daylight in the 24-hour day. Polar day (midnight sun) and polar night are detected and labelled automatically.
What the Calculator Shows
- Sunrise and Sunset: The times when the upper limb of the sun crosses the horizon, accounting for atmospheric refraction (standard zenith angle of 90.833°). Times are shown in local time based on your UTC offset.
- Solar Noon: The moment when the sun reaches its highest point in the sky — exactly halfway between sunrise and sunset. This is when shadows are shortest and solar panels produce maximum power.
- Day Length and Night Length: The duration of daylight and darkness in hours, minutes, and seconds. These sum to exactly 24 hours.
- Maximum Solar Elevation: The angle of the sun above the horizon at solar noon, in degrees. This determines shadow length, solar panel efficiency, and UV intensity at your location on the given date.
Polar Day and Polar Night
At latitudes above approximately 66.5° (Arctic Circle) or below −66.5° (Antarctic Circle), the sun can remain above or below the horizon for 24 hours on certain dates. Polar day (midnight sun) occurs in summer when the sun never sets — the astronomy day length calculator detects this and reports a day length of 24 hours. Polar night occurs in winter when the sun never rises — the calculator reports a day length of 0 hours. The exact dates of polar day and polar night depend on the specific latitude. For example, Tromsø, Norway (69.6°N) experiences polar night from late November to mid-January and midnight sun from late May to mid-July.
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Frequently Asked Questions About Astronomy Day Length Calculator
Common questions about sunrise, sunset, and day length calculations
An astronomy day length calculator computes sunrise, sunset, solar noon, and day length for any date and location using solar position algorithms. Our calculator uses the NOAA algorithm based on Jean Meeus's Astronomical Algorithms, accurate to within 1 minute for most locations. All calculations run locally in your browser — no signup required.
The NOAA solar position algorithm used by this calculator is accurate to within approximately 1 minute for locations between latitudes −65° and +65°. Accuracy decreases slightly at higher latitudes due to atmospheric refraction variations. The calculation uses a standard atmospheric refraction correction of 0.833° at the horizon.
Absolutely. The astronomy day length calculator runs entirely in your browser. Your latitude, longitude, and date inputs are never sent to any server, stored in a database, or tracked. If you use the "Use my current location" feature, your coordinates are only used locally for the calculation.
Yes — the astronomy day length calculator is 100% free with no signup, no account, and no usage limits. Calculate sunrise and sunset for any date and location, completely free forever with no ads.
Solar noon is the moment when the sun reaches its highest point in the sky — exactly halfway between sunrise and sunset. It is not necessarily at 12:00 local time because clock time is standardised to time zones while solar noon depends on your exact longitude. Solar noon is when shadows are shortest and solar panels produce maximum power.
Maximum solar elevation is the angle of the sun above the horizon at solar noon, measured in degrees. A value of 90° means the sun is directly overhead (only possible near the equator). Higher elevation means more intense sunlight, shorter shadows, and better solar panel performance. In winter at high latitudes, the maximum elevation can be very low (under 10°).
Midnight sun (polar day) occurs at high latitudes in summer when the sun stays above the horizon for 24 hours. Polar night occurs in winter when the sun stays below the horizon for 24 hours. The calculator detects both conditions automatically and displays a special message. These phenomena occur above the Arctic Circle (66.5°N) and below the Antarctic Circle (66.5°S).
Yes. The astronomy day length calculator works for any date — past, present, or future. The solar position algorithm is valid for dates from approximately 1000 CE to 3000 CE. Historical and future sunrise/sunset times are calculated with the same accuracy as current dates.
The UTC offset converts the calculated UTC times to your local time zone. The solar calculation always produces times in UTC (Coordinated Universal Time). Enter your local UTC offset (e.g. −5 for New York EST, +5.5 for India, +9 for Japan) to see sunrise and sunset in your local time. The offset does not affect the calculation — only the display.