How Long After Sunset Does It Get Dark? Six-City Reference

There is no single wait after sunset. In this calculation for six US city centers across 2026, civil twilight ends about 25–38 minutes after sunset. Astronomical twilight ends about 82–158 minutes after sunset. These are two different milestones; neither predicts exactly how dark your surroundings will look.

Choose the milestone that matches your question, then compare your city and season below. The tables describe modeled solar positions over a level horizon. Clouds, hills, buildings, the Moon and city lights are outside the calculation.

What does “dark” mean after sunset?

The US Naval Observatory and National Weather Service define evening twilight by the Sun's center below the horizon:

“Dusk” alone can be ambiguous. Use civil dusk, nautical dusk or astronomical dusk when you need a specific threshold. The three durations below all start at sunset. Do not add the columns together.

Minutes after sunset, by city

The range for each city covers every sunset date from 1 January through 31 December 2026. Values are rounded to the nearest whole minute. Each city uses the same representative center point as the site's sun-time lookup.

These are annual ranges, not a promise that a date will be near the middle of its city's range. For a particular evening, use the dated rows in the download. A month's minimum and maximum are also available in the summary.

For example, Portland's calculated interval to astronomical dusk ranges from about 98 to 158 minutes during this year. San Diego's range is about 82 to 102 minutes. A single “90 minutes after sunset” rule misses part of both ranges.

A summer evening in Portland, step by step

At the disclosed Portland, Oregon center point on 21 June 2026, the model gives these local clock times in America/Los_Angeles:

The interval uses the underlying event instants before the displayed clock times are rounded. Subtracting rounded clock labels can differ by a minute from the rounded elapsed duration.

All four UTC timestamps fall on 22 June, while their Portland local dates are 21 June. The download keeps both forms so a UTC date is not mistaken for the date of the local evening. Each event is converted using its city's time zone; daylight saving changes the clock label, not an elapsed interval between fixed instants.

Compare four dates in the year

These are four stated calendar dates, not exact equinox or solstice instants. Every number is cumulative minutes after sunset, rounded to a whole minute.

The full-year table, rather than these four samples alone, supplies the annual ranges. The changing geometry of the evening Sun makes the interval depend on latitude and date. The result for one city or season should not be applied to every location.

Is astronomical dusk a guarantee of a black sky?

No. It is a solar-position boundary. The National Park Service describes natural nighttime light from the Moon, stars and airglow. Artificial light and atmospheric conditions can also affect what you see. This reference does not model any of those conditions or predict whether a particular star, camera exposure or trail will be visible.

Use the named twilight boundary for a clear statement of timing. For an actual outing, also check the conditions and requirements of the location. These tables do not establish legal lighting rules or a safe time to navigate or hike.

How this reference was calculated and checked

Sunset Today computed 2,190 city/date rows, containing 8,760 event instants and 6,570 sunset-to-twilight intervals, using SunCalc 1.9.0. Coordinates, year, thresholds and zero observer height are frozen in version 1.0.0. No weather observations or private visitor data are used.

The formula for each interval is the twilight-end UTC instant minus the sunset UTC instant, divided by 60 seconds. Event ordering and the local date of every sunset were checked. A Python standard-library translation reproduced all 8,760 instants within 0.002 seconds. That verifies reproduction of the same equations; it does not independently establish astronomical accuracy.

A separately implemented geometric solar-altitude solver using the NOAA/Meeus equations checked 24 city/date rows: the six cities on the four dates above. Its largest event-time difference was 2.919 minutes; the largest difference in a sunset-to-twilight duration was 0.279 minutes. These are conservatively rounded model differences for the disclosed sample, not a confidence interval or an observed-sky error bound. NOAA notes that its online calculator is no longer actively maintained. No official certification is claimed.

Download, reproduce or cite

Version 1.0.0, prepared 26 October 2026. The reference year is 2026. Save the data together with the methodology and limitations; keep the version and the definition of twilight with any quoted result.

• cities-v1.json: the six coordinate and time-zone inputs.
• daily-v1.csv: every date, four UTC and local event times, and three elapsed intervals.
• summary-v1.json: annual and monthly ranges plus the four-date examples.
• methodology-v1.json: thresholds, calculation and rounding conventions.
• sources-v1.json: authoritative definitions and the pinned model.
• validation-v1.json: reproduction and separate-model comparison results.
• limitations-v1.json: interpretation and coverage limits.
• reproduce-v1.py: standard-library reproduction and sample comparison script.

Put the downloads in one folder and run python3 reproduce-v1.py. The script checks the daily table and prints the validation report; it does not contact a live service.

Suggested reference: Sunset Today. How Long After Sunset Does It Get Dark? Six-City Reference. Version 1.0.0, 26 October 2026. Cite the relevant city, year and twilight boundary alongside a number. Report a possible error through Contact, including the version, city and local date.

Check sunset for your date

The site's sun-time lookup shows sunrise, sunset and the month calendar for the supported cities. This reference supplies the separate, frozen twilight comparison; it does not add a live twilight or weather forecast to the lookup.