Daylight Calculator - Sunrise And Day Length

The daylight calculator estimates how long the Sun is above the apparent horizon for a chosen date and location. Enter the calendar date, latitude, longitude, and UTC offset, and the calculator returns daylight duration, sunrise, sunset, solar noon, solar declination, and a status label for normal sunrise, midnight sun, or polar night.

• • Fieldwork and class planning: Check whether an outdoor lab, survey, observation, or campus event has enough natural light without relying on a city-only almanac.
• • Travel and photography schedules: Compare daylight at a destination before choosing hike start times, photography windows, or evening activities.
• • Season and latitude comparisons: Move the same date between northern and southern latitudes to see how solstice and equinox daylight changes.
• • Polar-region interpretation: Identify dates when the sunrise equation produces no ordinary sunrise or sunset because the Sun stays above or below the horizon.

Use the result as an astronomy and planning estimate, not as a legal sunrise record. A city almanac may include local horizon rules, elevation data, and daylight-saving conventions that a coordinate-only calculator cannot infer.

The duration itself depends on latitude and date. Longitude and UTC offset mainly place sunrise, sunset, and solar noon on the local clock, so two towns on the same latitude can have nearly the same day length while their clock times differ.

That distinction is useful when comparing places. A class can hold the date steady and change only latitude to see the seasonal effect, then hold latitude steady and change longitude to see why the same daylight span appears earlier or later on a clock.

When you need the star-clock version of the same sky-position problem, Sidereal Time Calculator compares Earth's rotation against the stars instead of the Sun.

The calculator follows NOAA-style solar-position equations. First it converts the date to day of year and fractional year, then estimates the equation of time and solar declination. Next it solves the sunrise hour angle at the apparent sunrise/sunset zenith and converts that angle into hours of daylight.

• latitude: Observer latitude in degrees. Positive values are north of the equator and negative values are south.
• solar declination: The Sun's angular position north or south of Earth's equator for the selected day.
• 90.833 degrees: The apparent sunrise/sunset zenith used to include an approximate correction for atmospheric refraction and the Sun's disk.
• hour angle: The angular distance between solar noon and sunrise or sunset. Earth turns about 15 degrees per hour, so the hour angle converts directly to time.

If the inverse-cosine argument is between -1 and 1, the result has one ordinary sunrise and one ordinary sunset. If the argument is below -1, the selected location is in continuous daylight for that date. If it is above 1, the result is polar night.

The equation uses an apparent horizon, so the number is closer to common almanac sunrise than to a center-of-Sun geometric crossing. It still assumes a flat, unobstructed horizon; terrain and high viewpoints can shift direct sunlight by minutes.

For clock times, longitude and equation of time place solar noon in UTC minutes, and the UTC offset moves that value to local civil time. Enter daylight saving time in the UTC offset yourself when the location observes it.

According to U.S. Naval Observatory Rise, Set, and Twilight Definitions, computational sunrise and sunset occur when the Sun's center has a geometric zenith distance of 90.8333 degrees.

According to U.S. Naval Observatory Computing Times of Rise, Set, and Twilight, the Explanatory Supplement to the Astronomical Almanac is an authoritative source for methods used to compute rise, set, and transit phenomena.

If your field notes also require compass correction at the same coordinates, Magnetic Declination Calculator handles the north-reference side of location planning.

Daylight math looks compact, but four astronomy ideas control nearly every result the page returns.

The equator stays close to a 12-hour day throughout the year, with apparent daylight a little longer because of the sunrise/sunset correction. Higher latitudes swing harder, so the same calendar date can mean very different planning windows in Miami, Oslo, and Sydney.

The concept cards are also a checklist for auditing an unusual answer. If daylight duration looks plausible but solar noon appears far from midday, check longitude and UTC offset first. If duration itself looks surprising, compare the latitude and solar declination signs; opposite signs usually mean winter-like daylight for that hemisphere.

For night observations after sunset, Moon Phase Calculator adds the lunar-calendar context that daylight duration alone cannot provide.

Use real coordinates and the correct civil-time offset for the date you care about. That is especially important near time-zone borders and during daylight saving time.

1. 1 Enter the date: Type the year, month, and day. The calculator checks leap years and rejects impossible dates.
2. 2 Enter latitude: Use positive degrees for north latitude and negative degrees for south latitude.
3. 3 Enter longitude: Use positive degrees east of Greenwich and negative degrees west of Greenwich.
4. 4 Set UTC offset: Use the local clock offset for that date, such as -4 for Eastern Daylight Time or -5 for Eastern Standard Time.
5. 5 Read the status label: Normal means the sunrise and sunset times are usable estimates; midnight sun and polar night mean ordinary times do not exist for the selected date.
6. 6 Apply the caveats: Adjust your plan if mountains, buildings, elevation, weather, or a legal sunrise definition matters.

For a summer outdoor lab in New York, use the daylight calculator with 2026-06-21, latitude 40.7128, longitude -74.006, and UTC offset -4. The result gives about 15 hr 6 min of daylight, so a 7 PM field session still has natural light but is close enough to sunset that backup lighting may be sensible.

For a winter comparison, keep the New York coordinates and change the date to 2026-12-21 with UTC offset -5. The result drops to a little over 9 hours, which explains why field courses and solar demonstrations need a larger December buffer.

Greenhouse and plant-light users can pair the day-length result with Daily Light Integral DLI Calculator to translate light duration and intensity into plant exposure.

A coordinate-based daylight result helps when a broad city lookup is too coarse or when you want to compare several dates quickly.

• • Plan outdoor work with a real daylight window: The hours-and-minutes output gives a practical span for surveys, photography, field classes, or site visits.
• • Separate duration from clock time: Daylight duration is driven by date and latitude, while longitude and UTC offset explain why the clock times shift.
• • Spot polar edge cases: The status label prevents misleading sunrise or sunset times when the Sun never rises or never sets.
• • Teach the formula inputs: Solar declination and equation-of-time outputs make the result easier to audit in astronomy, geography, and physics lessons.
• • Compare seasons without changing tools: Move the same coordinates from March to June to December and see how the day-length curve changes.

The calculator is useful for sanity checks. If a result shows a very late solar noon, the longitude and time-zone pairing probably deserves a second look before you use the sunrise and sunset times in a schedule.

Because the output includes both duration and clock times, it can separate two common questions. "How much light is available?" is answered by daylight hours. "When does that light fall during the day?" is answered by sunrise, sunset, and solar noon. Keeping those answers separate helps prevent schedule mistakes near the edge of a time zone.

When the daylight window becomes an outdoor exposure plan, Sunscreen Calculator helps size the UV side of the same day.

The formula is deterministic, but the real horizon is not. These factors explain why an observed sunrise can differ from the calculated clock time.

• • The page assumes a standard apparent horizon and NOAA's 90.833 degree correction; it does not model elevation, mountain skylines, sea-level dip, or local obstructions.
• • For civil decisions, legal records, aviation, litigation, and safety-critical work, use the relevant official almanac or agency source instead of a general web calculator.
• • Time-zone rules are not inferred automatically. Enter the UTC offset for the actual date, including daylight saving time where it applies.

NOAA's published caveats matter most near the poles, where the Sun meets the horizon at a shallow angle and small atmospheric differences can create larger timing differences.

Time-zone handling is another practical limit. The calculator accepts a UTC offset because the offset is a civil rule, not an astronomy result. If a location changed daylight-saving rules, or if a historical date used a different standard offset, verify the local offset before treating the displayed clock times as a planning reference.

According to U.S. Naval Observatory Duration of Daylight/Darkness Table, its data services include a Duration of Daylight and Darkness Table for one year.

If the clock offset is the uncertain input, Time Zone Converter is the closer companion check before comparing sunrise and sunset across cities.