Daylight Length Calculator

Daylight length (also called day length or photoperiod) is the duration between sunrise and sunset on a given day at a specific location. It's measured as the time elapsed from the moment the upper edge of the sun appears above the horizon (sunrise) to when it completely disappears below the horizon (sunset). This duration excludes twilight periods like civil twilight, nautical twilight, and astronomical twilight. Day length varies throughout the year due to Earth's axial tilt of approximately 23.5° relative to its orbital plane.

Daylight hours change because Earth's axis is tilted at 23.5° relative to its orbit around the Sun. As Earth travels around the Sun, different hemispheres receive varying amounts of direct sunlight. During summer in a given hemisphere, that hemisphere tilts toward the Sun, resulting in longer days and shorter nights. During winter, it tilts away, causing shorter days. The equinoxes (around March 20 and September 22) are when day and night are approximately equal everywhere on Earth. The solstices mark the longest day (summer solstice, around June 21 in the Northern Hemisphere) and the shortest day (winter solstice, around December 21).

Latitude has a dramatic effect on daylight duration. At the equator (0° latitude), day length stays relatively constant year-round at approximately 12 hours. As you move toward the poles, seasonal variation becomes more extreme. At 40° latitude, daylight ranges from about 9 hours in winter to 15 hours in summer. At 60° latitude, it ranges from about 5.5 hours to 18.5 hours. Above the Arctic Circle (66.5°N) and below the Antarctic Circle (66.5°S), you experience the "midnight sun" (24-hour daylight in summer) and "polar night" (24-hour darkness in winter).

Golden Hour is the period shortly after sunrise and before sunset when daylight is warmer and softer, with a golden-reddish hue. The sun is low (between 6° below and 6° above the horizon), producing long shadows and flattering light—ideal for photography. It typically lasts 20-60 minutes depending on latitude and season.

Blue Hour occurs just before sunrise and after sunset when the sun is between 4° and 6° below the horizon. The sky takes on deep blue tones while retaining some ambient light. This is also highly prized by photographers for its ethereal quality. Both golden and blue hours are calculated precisely by this tool using astronomical algorithms.

Dawn (civil dawn) is when the sun is 6° below the horizon and there's enough light for most outdoor activities without artificial lighting. Sunrise is the exact moment the sun's upper edge appears above the horizon. Sunset is when the sun's upper edge disappears below the horizon. Dusk (civil dusk) occurs when the sun reaches 6° below the horizon after sunset, marking the end of civil twilight. Beyond dusk is nautical twilight, then astronomical twilight, and finally true night.

This calculator uses the well-established SunCalc astronomical library, which employs precise algorithms based on the VSOP87 planetary theory. For most locations, sunrise and sunset times are accurate within ±1-2 minutes. Slight variations may occur due to atmospheric refraction (which bends sunlight slightly, making the sun visible even when geometrically below the horizon) and local topography (mountains, hills). The calculator accounts for standard atmospheric refraction. Time zone approximation uses longitude-based offset (UTC + round(lng/15) hours), which is accurate for most locations but may differ near time zone boundaries.

Polar day (midnight sun) and polar night occur within the polar circles (above 66.5° latitude). During polar day in summer, the sun stays above the horizon for 24 hours or more—it never sets. Conversely, during polar night in winter, the sun never rises above the horizon. The duration of these phenomena increases with latitude: at the Arctic Circle, you get about one day of midnight sun; at the North Pole, the sun stays up for about 6 months (from the March equinox to the September equinox). This calculator will indicate if your selected location and date experience either phenomenon.

This calculator displays approximate local time based on longitude. It does not automatically adjust for daylight saving time (DST) since DST rules vary by country, region, and year. The times shown represent standard solar time for the given longitude. If your location observes DST, you may need to add one hour during DST periods. The actual duration of daylight is unaffected by DST—only the clock representation changes. For example, if sunset is calculated at 7:00 PM standard time, it would be displayed as 8:00 PM during DST.