When Is Sunset Today? The Astronomy, Geometry, and Local Data Behind the Answer

Sunset today occurs at the moment the Sun's upper edge drops below your local horizon, and the exact clock time depends on your latitude, longitude, elevation, and the date. In the United States, that moment typically lands between roughly 4:30 p.m. and 8:30 p.m. local clock time depending on season and location. The only reliable answer for your address is a local almanac, a national observatory calculator, or a trusted weather service keyed to your coordinates.

What "Sunset" Actually Means at the Horizon

The astronomical definition is not the moment the Sun's center touches the horizon. Official almanac convention uses the upper limb of the solar disk, and it applies a standard atmospheric refraction correction of about 34 arcminutes. That combination means the Sun's geometric center is already roughly 50 arcminutes below the true horizon line when "sunset" is recorded.

Why does refraction matter so much? Earth's atmosphere bends light downward near the horizon, so we see the Sun slightly higher than it physically sits. At the horizon the bending is strongest, roughly half a degree, which is about the Sun's own apparent diameter. Without the correction, published sunset times would run several minutes late relative to what your eye sees.

The practical result is a soft, gradual event rather than an instant. The disk takes roughly two to three minutes to sink its own width below the horizon at mid-latitudes. That is why "sunset" is a moment on a table but a process on the sky.

The Geometry That Sets the Clock Time

Three geometric quantities drive the answer. First, the Sun's declination, its angular height above or below the celestial equator, shifts through the year by about 23.4 degrees. Second, your latitude fixes how that declination translates into a path across your sky. Third, your longitude sets when solar noon occurs at your location relative to your time zone's central meridian.

The hour angle formula ties these together. Sunset hour angle depends on latitude and declination through a cosine relationship that fails near the polar circles. When the combined term exceeds 1, the Sun never sets; when it drops below negative 1, the Sun never rises. That failure is not a bug in the math but a real boundary condition.

Longitude offsets are easy to underestimate. A one-degree longitude difference shifts local solar time by four minutes. Near a time zone boundary, two towns on the same latitude can see sunset 30 to 60 minutes apart purely because of where the zone line was drawn.

Plain language: the Sun sets when your patch of Earth rotates away from it, and the clock reading is a bookkeeping layer on top of that rotation.

Quantified Context: Ranges, Rates, and Seasonal Swing

Across the contiguous United States, sunset time swings widely through the year. At latitude 40 degrees north, the spread between the earliest winter sunset and the latest summer sunset is roughly 4.5 to 5 hours of clock time, partly inflated by daylight saving shifts. The underlying solar swing is closer to 2.5 to 3 hours between solstices at that latitude.

The daily change is fastest near the equinoxes. At mid-latitudes, sunset can move by 2 to 3 minutes per day around the March and September equinoxes. Near the solstices the rate flattens to under a minute per day, which is why late June sunsets feel stuck.

Latitude amplifies everything. Miami, near 26 degrees north, sees a much smaller seasonal swing than Seattle near 48 degrees north. Above the Arctic Circle, the Sun simply does not set for weeks in summer and does not rise for weeks in winter.

Elevation adds a small but measurable nudge. Standing 1,000 feet above a flat horizon pushes sunset roughly 1 to 2 minutes later, because you can see farther over the curve of the Earth. The effect grows with height and with unobstructed terrain.

Edge Cases That Break Simple Calculators

Coastal west-facing horizons deliver later sunset than a flat inland horizon at the same coordinates. A hill or mountain to your west can pull sunset earlier by several minutes to more than an hour, depending on angular height. Most online calculators ignore terrain entirely.

Atmospheric conditions shift the observed moment too. Unusually cold air near the surface increases refraction and can make the Sun appear to set slightly later than predicted. Warm, hazy air does the opposite. These effects are small but real, typically under a couple of minutes.

Polar day and polar night are the hardest cases. Within roughly 66.5 degrees latitude, some dates have no sunset at all, and calculators may return an error or a placeholder. The boundary is not fixed because refraction and the Sun's finite disk push the practical polar circle slightly farther toward the equator.

Time zone politics add another layer. Some regions use daylight saving time, some do not, and a few have shifted zone boundaries by law. A sunset time is only meaningful alongside the time zone and offset it assumes.

Published tables use the upper limb, not the center, so a phone app showing "solar center" will read a minute or two different. Terrain, buildings, and trees are never in the almanac model; your actual horizon can shift sunset by tens of minutes. Refraction corrections assume standard atmosphere, so extreme weather or altitude can move the observed time. Daylight saving transitions change the clock reading, not the physical event. Polar latitudes may have no valid sunset time on a given date, so treat errors as meaningful.

Misconceptions Worth Correcting

Many people assume sunset time is the same everywhere in a time zone. It is not. Longitude within a zone, latitude, and elevation all vary, so a single zone-wide sunset figure is an average at best.

Another common belief is that the earliest sunset falls on the winter solstice. It usually does not. Because of the equation of time, a mismatch between mean solar time and true solar time, the earliest sunset at mid-northern latitudes typically arrives in early to mid-December, days before the solstice. The latest sunrise lands in early January. This counterintuitive offset surprises even careful observers.

People also confuse civil twilight with sunset. Civil twilight ends when the Sun is 6 degrees below the horizon, roughly 20 to 30 minutes after sunset at mid-latitudes. That is the practical limit for most outdoor activity without artificial light, and it is a different number from sunset itself.

Practical Actions for an Accurate Local Time

Use a source keyed to coordinates, not a city name. Observatory calculators and national weather services accept latitude and longitude and apply the standard refraction and limb conventions. City-level tables can be off by minutes near coastlines and terrain.

Step one: confirm your exact coordinates to at least two decimal places. Step two: check whether the tool reports upper-limb or center-of-disk sunset. Step three: note the time zone and daylight saving status the tool assumes. Step four: subtract or add for your local horizon if a ridge or building blocks the west. Step five: cross-check against a second authoritative source if the time matters for photography, aviation, or event planning.

For planning, treat civil twilight end as your real "dark enough" threshold. For safety-critical outdoor work, add a buffer of 30 minutes before sunset rather than cutting it close. One unit system applies throughout: US customary feet for elevation and miles for distance.

A Sunset Timeline Through One Evening

Limitations and What Tables Cannot Tell You

No published sunset time accounts for your personal horizon. A west-facing ridge, a treeline, or a city skyline changes the observed moment more than most atmospheric corrections do. If the precise second matters, observe your own horizon and calibrate against a calculator over several clear evenings.

Refraction models assume a standard atmosphere. Extreme cold, unusual pressure gradients, and elevated observing sites shift the correction slightly. These effects are usually under two minutes but are not zero.

The math also assumes a spherical Earth with a standard horizon dip. That is accurate enough for civil purposes but breaks down at very high altitude or over very long sightlines. For those cases, a terrain-aware simulation is the appropriate tool.

Finally, clock time is political, not astronomical. Legal time zone changes, daylight saving rules, and local boundary decisions can alter the reading without changing the sky. Always pair a sunset time with the time standard it uses so the number stays meaningful.