In 1928, the International Astronomical Union introduced the term Universal Time for GMT beginning at midnight.
Universal Time is now determined by reference to distant celestial objects: UTC is derived from International Atomic Time (TAI), and is adjusted by leap seconds to compensate for variations in the rotational velocity of the Earth.
People in Antiquity divided the day into twelve hours, but these were reckoned from sunrise rather than midnight.
The Horae, literally "the hours," were the original Greek goddesses who oversaw regulated life.
The Matins, the nocturnal prayer is, according to the Rule of Saint Benedict, to be prayed at the "eighth hour of the night", which corresponds to about 2 am.
The Spanish siesta derives its name from the Latin hora sexta for the sixth hour (noon).