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Most other languages lack formal abbreviations for "before noon" and "after noon", and their users use the 12-hour clock only orally and informally. [citation needed] However, in many languages, such as Russian and Hebrew, informal designations are used, such as "9 in the morning" or "3 in the night".
Noon (also known as noontime or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 midday), 12 p.m. (for post meridiem, literally "after midday"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 (military time). Solar noon is the time when the Sun appears to contact the local celestial meridian.
Twilight occurs according to the solar elevation angle θ s, which is the position of the geometric center of the Sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon).
Dawn begins with the first sight of lightness in the morning, and continues until the Sun breaks the horizon. The morning twilight is divided in three phases, which are determined by the angular distance of the centre of the Sun (degrees below the horizon) in the morning. These are astronomical, nautical and civil twilight.
The night length is inconsistent during a year. The nineteenth volume of the Book of Sui says that at the winter solstice, a day was measured to be 60% night, and at the summer solstice, only 40% night. [10] The official start of night thus had a variation from 0 to 1 gēng. This variation was handled in different ways.
Dr Feifei Bu, from UCL’s department of behavioural science and health, said: “Our findings suggest that on average, people’s mental health and wellbeing are better in the morning and worst ...
More blue light is scattered, so if the sun is present, its light appears more reddish. In addition, the sun's low angle above the horizon produces longer shadows. The term hour is used figuratively; the effect has no clearly defined duration and varies according to season and latitude.
Blue hour at the Old Cathedral of the Holy Name of Jesus, Bragança in Portugal. The blue hour (from French l'heure bleue; [1] [a] pronounced [lœʁ blø]) is the period of twilight (in the morning or evening, around the nautical stage) when the Sun is at a significant depth below the horizon.