Dictionary term
Day Length
Direct answer
Day Length is the interval between defined sunrise and sunset for a location and date, shaped mainly by latitude, season, and the adopted rise-and-set convention.
Day Length is the elapsed time from local sunrise to local sunset.
Day Length is the elapsed time from local sunrise to local sunset.
A Sun–Earth orientation for seasonal, atmospheric, tidal, and terrestrial terms.Quick reference
- Use when
- Use Day Length with location, date, and the definition used; distinguish daylight from civil or astronomical twilight.
- Do not use it for
- Do not report one day length for an entire country or confuse daylight with sunshine duration under clouds.
- Reference category
- Seasons & Earth Almanac
- Related terms
- Astronomical Season, Meteorological Season, Equinox, Solstice
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The story behind Day Length
Comparing changing daylight has guided calendars and seasonal work since long before precise clocks.
Day Length in spiritual tradition
Day length makes the seasonal breathing of a place measurable.
Day Length: fact and faith, kept distinct
This is a factual astronomy, calendar, Earth-science, cultural, or historical reference. It can support wonder at the created order without becoming a claim of fate, worship, or private revelation.
Day Length in numerology
Day Length is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Day Length matters
Day length is one of the clearest seasonal signals and affects ecosystems, agriculture, energy use, and daily routines.
Day Length at work: an example
Near an equinox, calculated daylight can still exceed twelve hours because sunrise and sunset use the Sun's upper edge and include refraction.
Where interpretation stops
Day Length is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: Length of Day and Night at the Equinoxes - Official explanation of equinox geometry and why observed daylight is not exactly twelve hours.
- U.S. Naval Observatory: Astronomical Information Center - Official index for time, calendars, seasons, coordinates, and observable sky phenomena.
- Source
- The Great Almanac Dictionary
- Category
- Seasons & Earth Almanac
- Also appears in
- Seasons & Earth Almanac
- Aliases
- None listed
- Last updated
- 2026-07-15
Track changing daylight
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More in Seasons & Earth Almanac
- Inferior Mirage
- Nautical Dawn
- Polar Day
- Solar Insolation
- Sunset
- Anticrepuscular Rays
- Circumzenithal Arc
Common questions
What is Day Length?
Day Length is the interval between defined sunrise and sunset for a location and date, shaped mainly by latitude, season, and the adopted rise-and-set convention.
How is Day Length used in an almanac?
Use Day Length with location, date, and the definition used; distinguish daylight from civil or astronomical twilight.
What should I avoid when interpreting Day Length?
Do not report one day length for an entire country or confuse daylight with sunshine duration under clouds.
