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24-hour clock. A public 24-hour clock in Curitiba, Brazil, with the hour hand on the outside and the minute hand on the inside. The modern 24-hour clock is the convention of timekeeping in which the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours (and minutes) passed since midnight, from 00 (:00 ...
An alternate orthography for the numerical part includes 24×7 (usually pronounced "twenty-four by seven"). The numerals stand for "24 hours a day, 7 days a week". Less commonly used, 24/7/52 (adding "52 weeks") and 24/7/365 service (adding "365 days") make it clear that service is available every day of the year.
An hour (symbol: h; [1] also abbreviated hr) is a unit of time historically reckoned as 1 ⁄ 24 of a day and defined contemporarily as exactly 3,600 seconds . There are 60 minutes in an hour, and 24 hours in a day. The hour was initially established in the ancient Near East as a variable measure of 1 ⁄ 12 of the night or daytime.
Day. A quarter-day cycle at Midtown Manhattan, from afternoon to dusk. 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, noon, afternoon, evening, and night.
Note that this definition refers to the use of a complete circular dial to represent a 24-hour day. Using the numbers from 0 to 23 (or 1 to 24) to mark the day is the 24-hour clock system. Sundials use 24-hour analog dials—the shadow traces a path that repeats approximately once per day. Many sundials are marked with the double-XII or double ...
Earth-based: the day is based on the time it takes for the Earth to rotate on its own axis, as observed on a sundial [citation needed]. Units originally derived from this base include the week (seven days), and the fortnight (14 days). Subdivisions of the day include the hour (1/24 of a day), which is further subdivided into minutes and seconds ...
USNO article on the definition of seconds and leap seconds Archived 2012-06-11 at the Wayback Machine; A history of astronomical time scales by Steve Allen; Why is a minute divided into 60 seconds, an hour into 60 minutes, yet there are only 24 hours in a day Ask the Experts – March 5, 2021. SCIENTIFIC AMERICAN
The large dial shows the ten hours of the decimal day in Arabic numerals, while the small dial shows the two 12-hour periods of the standard 24-hour day in Roman numerals. Decimal time is the representation of the time of day using units which are decimally related. This term is often used specifically to refer to the French Republican calendar ...