Day
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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. As a day passes at a given location it experiences morning, noon, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.
Decimal clock face, made in around the start of the 19th century
Night in art
Image: Midtown Manhattan from Weehawken September 2021 panorama 1
Image: Midtown Manhattan from Weehawken September 2021 panorama 2
Hour
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An hour is a unit of time historically reckoned as 1⁄24 of a day and defined contemporarily as exactly 3,600 seconds (SI). There are 60 minutes in an hour, and 24 hours in a day.
A 7th-century Saxon tide dial on the porch at Bishopstone in Sussex, with larger crosses marking the canonical hours.
Sundial with Italian hours in Asti
A Chinese diagram from Su Song's AD 1092 Xinyi Xiangfa Yao illustrating his clocktower at Kaifeng.
A reconstruction of another kind of Chinese clepsydra in Beijing's Drum Tower