The traditional
Chinese calendar
The traditional Chinese calendar (also known as the Agricultural Calendar 曆; 农历; ''Nónglì''; 'farming calendar' Former Calendar 曆; 旧历; ''Jiùlì'' Traditional Calendar 曆; 老历; ''Lǎolì'', is a lunisolar calendar ...
divides a year into 24
solar term
A solar term is any of twenty-four periods in traditional Chinese lunisolar calendars that matches a particular astronomical event or signifies some natural phenomenon. The points are spaced 15° apart along the ecliptic and are used by lunisolar ...
s. ''Lìdōng'', ''Rittō'', ''Ipdong'', or ''Lập đông'' () is the 19th solar term. It begins when the Sun reaches the
celestial longitude
Astronomical coordinate systems are organized arrangements for specifying positions of satellites, planets, stars, galaxies, and other celestial objects relative to physical reference points available to a situated observer (e.g. the true horizo ...
of 225° and ends when it reaches the longitude of 240°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 225°. In the
Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years dif ...
, it usually begins around November 7 and ends around November 22.
Lidong signifies the beginning of winter in East Asian cultures.
Pentads
*水始冰, 'Water begins to freeze' – the initial stages of water bodies freezing over.
*地始凍, 'The earth begins to harden'
*雉入大水為蜃, 'Pheasants enter the water for clams'
Date and time
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19
Winter time