How the day is measured
Sunrise and sunset are the moments the upper edge of the Sun touches the horizon. The Sun is actually a little below the true horizon at both instants: Earth's atmosphere bends its light by about half a degree, lifting the disk into view a couple of minutes early at dawn and holding it a couple of minutes late at dusk. This calculator includes that standard refraction, so the times match what you would actually see over a flat horizon. Solar noon is the midpoint, when the Sun is highest and due south (or due north from the southern hemisphere), and the day length is simply the time from sunrise to sunset.
The three twilights
The sky does not snap from day to night at sunset. It fades through three named stages, each defined by how far the Sun has sunk below the horizon:
- Civil twilight (Sun 0 to 6 degrees down): bright enough to read or walk outside without lights; the brightest planets and stars start to appear.
- Nautical twilight (6 to 12 degrees): the horizon at sea is still faintly visible, which once let sailors measure star altitudes; most stars are now out.
- Astronomical twilight (12 to 18 degrees): the sky looks dark to the eye, but a faint glow still lingers for telescopes. Once the Sun is more than 18 degrees down, it is true night.
Why the day's length changes
Day length swings through the year because Earth's axis is tilted about 23.4 degrees. In your summer the hemisphere leans toward the Sun, which climbs higher and lingers longer, so days stretch out; in winter it leans away and days shrink. The swing is gentle near the equator and dramatic toward the poles, where the Sun can stay up for a full 24 hours around midsummer (a polar day) or never rise at all in deep winter (a polar night). The tilt behind all of this is explained on Seasons & the Sun, and the reason clock noon drifts away from solar noon is the story of the equation of time.
See the rest of your sky
For tonight's Moon phase, where the planets sit and what is visible from your location, open Today in the Sky. To find the next eclipse visible from your spot, use the Eclipse & Saros Explorer, and to catch several planets at once, the Planet Parade Tracker.
Frequently asked questions
What time does the Sun rise and set today?
Enter your location (or tap Use my location) and the calculator shows today's sunrise, solar noon, sunset and total day length in your device's time zone, computed from the Sun's true position.
What is the difference between civil, nautical and astronomical twilight?
Civil twilight lasts until the Sun is 6 degrees below the horizon (you can still read outside), nautical twilight until 12 degrees (the horizon is still faintly visible at sea), and astronomical twilight until 18 degrees, after which the sky is fully dark.
Why is the day longer in summer?
Earth's axis is tilted about 23.4 degrees, so in summer your hemisphere leans toward the Sun, the Sun climbs higher and stays above the horizon longer, giving more daylight; in winter it leans away and days are short.
What are the golden hour and blue hour?
Golden hour is the period of warm, soft light when the Sun is between about 6 degrees above the horizon and the horizon itself, ideal for photography. Blue hour is the cooler twilight just after sunset or before sunrise, when the Sun is roughly 4 to 6 degrees below the horizon. This page lists both for your morning and evening.
Keep exploring
Today in the Sky
The Moon's phase, the planets' places and tonight's highlights at a glance.
InteractiveSeasons & the Sun
How the 23.4-degree tilt makes the solstices, equinoxes and the long days of summer.
InteractiveEquation of Time
Why a sundial runs ahead of and behind the clock, and the analemma.
SkyEclipse & Saros Explorer
The next solar and lunar eclipses, and the next one visible from your location.