Day Length, Golden Hour & Twilight
Last reviewed: April 2026
A sunrise and sunset calculator provides the exact times of sunrise, sunset, and twilight for any location and date. It also shows day length, solar noon, and golden hour times — useful for photography, outdoor planning, agriculture, and travel.
This calculator uses the NOAA Solar Position Algorithm, which computes the sun's position based on the date, latitude, and longitude. The algorithm accounts for Earth's elliptical orbit, axial tilt (23.44°), and the equation of time (the difference between solar time and clock time caused by orbital eccentricity and axial tilt). Results are accurate to within 1–2 minutes for most locations. Atmospheric refraction, which bends sunlight at the horizon and makes the sun appear to rise slightly earlier and set slightly later than geometric calculations suggest, is included using the standard refraction correction of 0.833°.
At the equator, day length stays close to 12 hours year-round. As you move toward the poles, seasonal variation increases dramatically. In New York (40.7°N), day length ranges from about 9 hours 15 minutes at the winter solstice to 15 hours 6 minutes at the summer solstice — a swing of nearly 6 hours. In Anchorage, Alaska (61°N), the range is roughly 5.5 hours to 19.5 hours. Above the Arctic Circle (66.5°N), there are periods of continuous daylight in summer and continuous darkness in winter. The calculator handles these polar extremes and will show "Polar Day" or "Polar Night" when applicable.
The golden hour is the period when the sun is between 0° and 6° above the horizon — roughly the first and last hour of sunlight each day. During golden hour, sunlight travels through more atmosphere, filtering out blue wavelengths and producing warm, golden tones with long, soft shadows. Photographers, filmmakers, and real estate agents prize this light for its flattering quality. The calculator shows both morning and evening golden hour windows. At higher latitudes in summer, golden hour can last significantly longer than one hour.
Civil twilight (sun 0–6° below horizon): bright enough for most outdoor activities without artificial light. Nautical twilight (6–12° below): the horizon is still visible at sea, useful for navigation. Astronomical twilight (12–18° below): the sky is dark enough for most astronomical observations. True astronomical darkness only occurs when the sun is more than 18° below the horizon. In summer at high latitudes, the sun may never dip below 18°, meaning there's no true darkness — this phenomenon is the famous "white nights" of St. Petersburg and Scandinavian cities.
| Latitude | City Example | Day Length |
|---|---|---|
| 0° (Equator) | Quito | ~12 hours |
| 30°N | Cairo | ~14 hours |
| 40°N | New York | ~15 hours |
| 50°N | London | ~16.5 hours |
| 60°N | Helsinki | ~19 hours |
| 66.5°N | Arctic Circle | 24 hours |
Earth's axial tilt of approximately 23.44° relative to its orbital plane is the fundamental reason sunrise and sunset times change throughout the year. During summer in the Northern Hemisphere, the North Pole tilts toward the sun, causing the sun to follow a higher arc across the sky and remain above the horizon for longer. At the summer solstice (around June 20-21), locations above the Arctic Circle experience 24 hours of continuous daylight, while locations below the Antarctic Circle experience 24 hours of darkness. The reverse occurs at the winter solstice (around December 21-22). At the equator, day length remains close to 12 hours year-round because the tilt has minimal effect at 0° latitude.
Atmospheric refraction adds approximately 2 minutes to the observed day length by bending sunlight around Earth's curvature. When the sun appears to touch the horizon, its physical center is actually about 0.83° below it — the atmosphere acts like a lens, curving the light so we see the sun slightly higher than its geometric position. Temperature inversions, humidity, and altitude all affect the degree of refraction. At extremely cold temperatures (common in polar regions), refraction can be so strong that the sun appears above the horizon even though it is geometrically well below it, a phenomenon called the Novaya Zemlya effect.
The rate of change in day length depends on both the time of year and the latitude. Near the equinoxes (March and September), day length changes most rapidly — locations at mid-latitudes gain or lose 2-4 minutes of daylight per day. Near the solstices, the rate of change slows to nearly zero as day length reaches its maximum or minimum. At 45°N latitude, the difference between the longest and shortest days is approximately 6 hours and 40 minutes. At 60°N (roughly the latitude of Helsinki or Anchorage), this difference exceeds 12 hours, with the longest day lasting nearly 19 hours and the shortest just under 6 hours.
Elevation above sea level also affects sunrise and sunset times. At higher elevations, the observer can see further around Earth's curvature, causing the sun to appear earlier and set later. A person standing at sea level sees sunrise approximately 2 minutes later than someone at 1,000 meters elevation at the same latitude and longitude. This is why mountain peaks catch sunlight long before valleys, and why pilots at cruising altitude (10,000+ meters) can witness sunsets that have already ended for people on the ground below.
Photographers rely on precise sunrise and sunset times to plan shoots during golden hour — the period roughly 20-30 minutes after sunrise and before sunset when sunlight travels through more atmosphere, producing warm tones and soft shadows. Blue hour, the period of twilight before sunrise and after sunset when the sky takes on deep blue hues, lasts approximately 20-40 minutes depending on latitude and season. Solar panel installers use day length and sun angle data to calculate expected energy generation and optimal panel tilt angles throughout the year. Outdoor event planners, construction crews, and agricultural operations all schedule activities around available daylight, particularly in high-latitude locations where winter daylight hours are severely limited.
Religious observances in Islam, Judaism, and other traditions define prayer times or fasting periods relative to sunrise, sunset, and twilight phases. Islamic daily prayers use specific sun positions: Fajr begins at dawn twilight (when the sun is 18° below the horizon), Dhuhr at solar noon, Asr in the mid-afternoon, Maghrib at sunset, and Isha when twilight ends. Jewish Shabbat begins at sunset on Friday and ends when three stars are visible on Saturday evening. Accurate sunrise and sunset calculations are therefore essential tools for religious communities worldwide, particularly at high latitudes where standard approximations can produce significant errors.
Daylight exposure directly regulates the human circadian rhythm through photoreceptive ganglion cells in the retina that respond to blue-wavelength light. Morning sunlight exposure triggers cortisol release (promoting alertness) and suppresses melatonin production, while the absence of sunlight in the evening allows melatonin to rise, promoting sleep. Seasonal Affective Disorder (SAD) affects an estimated 5% of the US population and is strongly correlated with latitude and winter day length — prevalence is approximately 1% in Florida but 9% in Alaska. Light therapy lamps (producing 10,000 lux of broad-spectrum light) are the standard first-line treatment, mimicking the intensity and spectrum of morning sunlight during months when natural daylight is insufficient.
Agricultural planning has depended on precise sunrise and sunset knowledge for millennia. Photoperiodism — the physiological response of plants to day length — determines when crops flower, fruit, and become dormant. Short-day plants like soybeans and chrysanthemums flower when daylight drops below a critical threshold, while long-day plants like wheat and lettuce flower when daylight exceeds their threshold. Greenhouses manipulate artificial lighting based on these photoperiod requirements to grow crops out of season. Livestock farmers also track day length because egg production in chickens drops significantly when daylight falls below 14 hours, which is why commercial poultry operations use supplemental lighting during winter months to maintain year-round productivity.
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→ Explore related tools. Check the related calculators section below for tools that complement this one — many calculations work best in combination.
See also: Moon Phase Calculator · Time Zone Converter · World Clock · Printable Calendar · Date Difference Calculator