Sunrise and Sunset Time Calculator

Sunrise and sunset times are critical for navigation, aviation, sailing, photography, and outdoor planning. Times vary by latitude, longitude, and date.

The key factors:

• Latitude: The closer to the poles, the more extreme the seasonal variation. At the equator, day length is nearly constant at 12 hours year-round. At 60°N in summer, the sun may set well past 22:00.
• Longitude: Determines your position within a time zone. Two cities in the same time zone but far apart in longitude can have sunrise times that differ by 30+ minutes.
• Date: The Earth’s axial tilt (23.5°) causes the seasons. At the summer solstice (around June 21 in the northern hemisphere), the sun rises earliest and sets latest.

Civil twilight: Begins when the sun is 6° below the horizon. There is enough light to see clearly, but the sun is not yet visible. Many aviation regulations use “civil twilight” as the boundary for VFR flight and navigation lights.

Nautical twilight: sun 12° below the horizon. The sea horizon is still just visible against the sky while the brighter stars are out, which is the narrow window when a sextant works. That overlap is the whole reason the category has a name.

Astronomical twilight: sun 18° below. Past this the sky is as dark as it will get. Above about 49° of latitude there are weeks in midsummer when it never arrives at all.

Golden hour: the sun between roughly 6° above the horizon and the horizon itself. Long shadows, warm light. Note that it is not literally an hour. Near the equator the sun drops through that band in about 25 minutes; at 60° in June it can crawl through it for well over two hours.

Blue hour: the sun between 4° and 8° below the horizon. The sky holds a deep even blue and city lights balance against it. Shorter than golden hour, and the reason landscape photographers are still standing there twenty minutes after sunset.

Day length formula (approximate): D = 24 − (24/π) × arccos((sin(p) + sin(lat) × sin(dec)) / (cos(lat) × cos(dec)))

Where p = +0.0145 radians (0.833°, the sun’s centre sitting just below the horizon once you allow for its radius and for atmospheric refraction), lat is your latitude, and dec is the solar declination for the date. Check the sign of p against a known case before trusting any version of this formula you find elsewhere: at the equator on an equinox it must give about 12.1 hours, not 11.9.

Everything on this page is a solar-position approximation good to a minute or two. That is fine for planning a shoot or a passage. For precise navigation, verify against official almanac data from the US Naval Observatory or the UK Hydrographic Office.