SunsetSunrise.org calculates solar events from a location, date and time zone. This page explains the definitions, display conventions and limits so you can interpret a result or compare it with another source.
Inputs and local time
The calculation uses latitude and longitude from the selected place or map point. A time-zone identifier determines the boundaries of the local calendar date and how event times appear on the clock. Browser geolocation supplies coordinates only when you request it and grant permission.
Local clock displays use the browser’s time-zone support, including applicable daylight-saving rules. If a lookup falls back to UTC, the displayed zone needs checking before you treat the time as a local schedule. Historical time-zone rules and far-future rules can also differ from present assumptions.
Sunrise and sunset
The solar-position model estimates the Sun’s geometric center. Sunrise and sunset are located where that center crosses an altitude of −0.833°. This conventional horizon offset approximates the Sun’s apparent radius and typical atmospheric refraction for a level, unobstructed horizon.
The model does not use your actual skyline, observer elevation, air pressure or temperature profile to adjust that event. It therefore predicts a standard astronomical time, not the exact second a particular mountain, tree line or building reveals or hides the Sun.
Twilight and photographic light windows
– Civil dawn and dusk: the Sun’s geometric center crosses −6°. – Nautical dawn and dusk: it crosses −12°. – Astronomical dawn and dusk: it crosses −18°. – Golden hour: this site’s chosen band is −4° to +6° in the morning and +6° to −4° in the evening. – Blue hour: this site’s chosen band is −6° to −4° in the morning and −4° to −6° in the evening.
The twilight boundaries are standard astronomical conventions. Golden hour and blue hour are photography terms without one universal definition; the bands above make this site’s windows reproducible. None of these angles guarantees a color or ground-level brightness.
How events and durations are found
The browser evaluates a compact solar-position model across the selected local day, searches for crossings of the relevant altitude and refines the crossing time. Results are displayed to the minute. That display precision is not a claim of minute-level observational accuracy.
Daylight duration totals time above the sunrise/sunset threshold within the local date. On an ordinary day, that is the interval from sunrise to sunset. This also allows continuous daylight, continuous darkness and dates containing only one crossing to be represented without inventing an event time. Rounded clock labels may not subtract to exactly the displayed duration.
A dash means that the relevant boundary was not found within the selected local date. The model’s finite sampling and standard atmospheric assumptions are less suitable for marginal horizon events near extreme latitudes. No globally validated error bound is claimed for this implementation.
Solar noon, position and the annual graph
The solar-noon card estimates the time of maximum solar altitude within the local day. This is close to upper meridian transit for ordinary days, but the terms are not strictly interchangeable in every polar circumstance. It is not a precision transit calculation.
Current Sun-position cards describe the present moment at the selected coordinates. Date-based sunrise, sunset and noon results follow the selected date. The daily arc is schematic. The annual daylight graph samples the 15th of each month and should not be read as a daily curve or an exact search for seasonal extremes.
Weather and location services
Current weather is supplied separately from Open-Meteo forecast-model data and is briefly cached by the site. Changing the solar date does not change that panel into historical weather or a forecast for the chosen date. Weather values are not inputs to the solar-event calculation.
The sources page identifies place-search, map and weather providers and links to the astronomical references. Those references explain conventions; they do not imply that a government agency operates, endorses or certifies this site.
Frequently asked questions
Why can a highly precise calculation disagree with what I see?
The actual horizon and atmospheric bending of light differ from standardized assumptions. More decimal places in a calculation cannot remove uncertainty about terrain or the atmosphere. Comparing observations requires the observer’s position and horizon conditions as well as a date.
Are times calculated for sea level or my actual elevation?
The horizon convention represents a level standard horizon. The tool does not apply a measured observer-elevation or terrain correction, even if your selected map point is on a mountain.
Is this a replacement for certified astronomical data?
No. It is a planning and educational calculator. If you need an authenticated result or a method with a stated accuracy requirement, use a service that explicitly provides that form of data.
What should I include when reporting a discrepancy?
Provide the coordinates, date, displayed time zone, event name and the result being compared. Include the comparison source’s elevation and event definition if available. Those details help distinguish different assumptions from a calculation problem.