Launching soon
Sunset Timer is a free, beautiful sunset and sunrise clock that launches soon. The preview on the right already computes tonight's times for your location, right in your browser. Leave your email and you will get one note the day it goes live.
One email, at launch. No spam, no newsletter, no daily mail. Just a heads up when the full sunset timer is ready.
The short answer
Sunset time is the moment the upper edge of the sun drops below your local horizon, and it depends on your latitude, longitude, and the date. Because of that, sunset tonight in your town can differ by a full hour or more from a city a few hundred miles away. This preview reads your browser location and computes tonight's sunset and sunrise for that exact spot. The finished Sunset Timer will let you search any city or ZIP, pick any date, and set a gentle reminder before the light turns.
Sunset feels like a fixed event, but the clock time of it changes every single day, and it changes by where you stand. The reason is geometry. The Earth is tilted on its axis by about 23.44 degrees, and it travels around the sun once a year. From the ground, that tilt makes the sun appear higher or lower in the sky depending on the season, which in turn moves the moments of sunrise and sunset earlier or later.
The math behind it is well established and needs no paid service. For any date, you first work out the solar declination, which is the sun's position north or south of the equator. Over the year that value swings between about -23.44 degrees and +23.44 degrees. From the declination and your latitude, you find the hour angle, the angle through which the Earth must turn to bring the sun to the horizon. Convert that hour angle to clock time and you have sunrise and sunset. This is the NOAA and U.S. Naval Observatory sunrise equation, rooted in the methods of Jean Meeus's Astronomical Algorithms.
One small correction matters a lot. Light bends as it passes through the atmosphere, so you see the sun slightly before it is geometrically at the horizon and slightly after it has dropped below. To account for this, sunrise and sunset are defined as the moment the center of the sun sits 0.833 degrees below the geometric horizon. That figure combines the sun's apparent radius with standard atmospheric refraction near the horizon. The preview applies this correction, which is why its times line up closely with an almanac. Between roughly 72 degrees north and south, the method is accurate to within about a minute.
For photographers, the most useful moments are not sunset itself but the soft windows around it. Golden hour is the period of warm, low-angle light in roughly the first hour after sunrise and the last hour before sunset. The exact length shifts with season and latitude. It is the light that flatters faces and landscapes, which is why it is also called the magic hour.
Blue hour is the cooler, even glow just before sunrise and just after sunset, when the sun is a few degrees below the horizon and the sky turns a deep cobalt. It is shorter than golden hour and beloved for cityscapes and calm water.
After the sun sets, darkness arrives in three measured steps, each defined by how far the sun has dropped below the horizon. The preview shows all three; the table below is the reference the finished guides will expand on.
| Twilight | Sun below horizon | What it means |
|---|---|---|
| Civil twilight | 6 degrees | Enough natural light for most outdoor activity. The cutoff hikers watch to be off the trail. |
| Nautical twilight | 12 degrees | The horizon is still faintly visible at sea. Brighter stars appear. |
| Astronomical twilight | 18 degrees | After this the sky is fully dark, which is what stargazers wait for. |
Two places can sit in the same time zone yet see sunset many minutes apart, because clock time is set by zone but the sun answers only to longitude and latitude. Move west within a zone and the sun sets later by the clock. Move toward the poles in summer and the day stretches long; move toward them in winter and it shrinks. Near the equator the day stays close to twelve hours all year, while higher latitudes see dramatic seasonal swings. This is exactly why a sunset timer should start from your real position rather than a generic city, and why the preview asks your browser for your location first.
Sunrise follows the same rules in mirror. Many people want both numbers in one glance: the runner planning a dawn loop with enough light, the angler reading the dawn and dusk windows, the traveler checking how long the evening will last. Sunrise is a first-class part of this tool, not an afterthought, which is why the preview shows tonight's sunset and this morning's sunrise side by side along with the length of the day.
The preview above shows tonight's sunset for your browser's location and today's date, with a live countdown. Because sunset depends on your exact latitude, longitude, and date, the time is specific to where you are right now. The finished site will let you check any city or ZIP and any date.
It uses the NOAA and U.S. Naval Observatory sunrise equation. The calculation finds the sun's declination for the date, then the hour angle at which the sun reaches the horizon for your latitude, and converts that to clock time. A 0.833 degree correction accounts for atmospheric refraction and the sun's apparent size.
The preview asks your browser for your location so it can compute times for your exact spot. The coordinates are used in your browser only and are not stored or sent anywhere. If you decline or your browser blocks it, the preview falls back to a default city and says so.
Golden hour is the stretch of warm, soft, low-angle light roughly in the first hour after sunrise and the last hour before sunset. Its exact length varies with season and latitude. Photographers favor it because the light is gentle and flattering.
Blue hour is the brief, even, cobalt-toned twilight just before sunrise and just after sunset, when the sun sits a few degrees below the horizon. It is shorter than golden hour and prized for cityscapes and reflections.
They are stages of fading light defined by how far the sun is below the horizon: civil twilight at 6 degrees, nautical twilight at 12 degrees, and astronomical twilight at 18 degrees. After astronomical twilight ends, the sky is fully dark.
Usable outdoor light fades at the end of civil twilight, about when the sun is 6 degrees below the horizon. True darkness for stargazing arrives at the end of astronomical twilight. The preview lists both dusk values for your location.
The Earth's axial tilt and its orbit around the sun shift the sun's apparent path through the year, so the declination changes daily. That moves sunrise and sunset a little earlier or later each day, with the largest swings at higher latitudes.
The underlying method is accurate to within about a minute between roughly 72 degrees north and south latitude. Local terrain, hills, and a high or low horizon can shift the moment you personally see the sun disappear by a few minutes.
Not yet. This is an early preview while the full Sunset Timer is being built. The preview already computes tonight's sunset and sunrise; the finished site will add city and ZIP search, any-date lookups, golden hour and blue hour detail, and optional sunset alerts. Leave your email and you will get one note at launch.
Be there at launch
One email, at launch. No spam and no newsletter, just a single heads up when the full site is ready.
You are trying an early preview
This sunset and sunrise tool is a sample while the site is being built, so the result may not be final. The finished site will add city and ZIP search, any date, golden hour and blue hour detail, and sunset alerts.