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A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.
Similar to the duration of night itself, the duration of twilight varies according to latitude. [19] At the equator, day quickly transitions to night, while the transition can take weeks near the poles. [19] The duration of twilight is longest at the summer solstice and shortest near the equinoxes. [20]
From their contents it is clear that the values for the duration of the light day and night were recorded during four colures aligned with the longest and shortest days of the year. [9] The records have gnomon tables, but they are preserved only for specific dates in the Hebrew calendar: the 15th of Nisan and the 15th of Tammuz.
Due to the continuous change of the duration of daylight over the course of the year, the duration of the day division, i.e. the temporal day hours and the temporal night hours, also changes over the year. The temporal hours of day and night are equal only at the spring and autumn equinoxes.
Systematically observing the sunrise, people discovered that it occurs between two extreme locations at the horizon and eventually noted the midpoint between the two. Later it was realized that this happens on a day when the duration of the day and the night are practically equal and the word "equinox" comes from Latin aequus, meaning "equal", and nox, meaning "night".
Daytime length or daytime duration is the time elapsed between beginning and end of the daytime period. Given that Earth's own axis of rotation is tilted 23.44° to the line perpendicular to its orbital plane , called the ecliptic , the length of daytime varies with the seasons on the planet's surface, depending on the observer's latitude .
The Talmudic hour is one twelfth of time elapsed from sunrise to sunset, day hours therefore being longer than night hours in the summer; in winter they reverse. The Indic day began at sunrise. The term hora was used to indicate an hour. The time was measured based on the length of the shadow at day time. A hora translated to 2.5 pe.
[3] [4] Photoperiodic flowering plants are classified as long-day plants or short-day plants even though night is the critical factor because of the initial misunderstanding about daylight being the controlling factor. Along with long-day plants and short-day plants, there are plants that fall into a "dual-day length category".