Chinese Lunar Calendar and the Twenty-Four Segments

chinese_calendar
Modern Chinese use two calendar systems. They use the Gregorian (Western / Yang) calendar to conduct official business, and to manage everyday life. At the same time, they use the Chinese (Lunar / Yin) calendar to determine the numerous celebration dates; to find out the dates of agriculture; and to calculate human fortunes with techniques like Zi Wei Dou Shu, Bazi, Chinese Gender Chart and Tik Pan San Sou.

Chinese calendar is based on the period of time that the moon needs to travel a full cycle (new, half and full and back). Therefore, it is also called lunar calendar. Like a Gregorian year, a normal Chinese year consists of twelve lunar months. However, as the moon only takes approximately 29 ½ days to complete a cycle, it makes the lunar year eleven days shorter than the Western calendar year. Every nineteen years, the western and chinese calendars sync up with the aid of seven lunar leap months. In other words, there are 7 lunar leap year (13 lunar month each) in a nineteen year cycle.

The use of the Chinese calendar dates back to 2600 B.C. when Emperor Huang Ti introduced the twelve periods of the zodiac to the Country. Later, Chinese astronomy further divides the a lunar year into twenty-four segments (table 1). Each segments are based on the longitude of the sun on the ecliptic, or solar terms, and therefore, the Chinese calendar also belongs to one of the lunisolar calendars. That is why the Winter Commences is always on Dec 21st or Dec 22nd, as it is the shortest day of the year; and the Summer Commences is always on Jun 21st or Jun 22nd, as it is the longest day of the year. The lunar calendar functions as a weather calendar for farmers, who use it to guide their crop planning in China.

Table 1 : Twenty-Four Segments of the Chinese Calendar

Chinese Name
English Translation
Date 1
Remark
立春
Spring Commences
5th Feb.
The begining of Spring
雨水
Spring Showers
19th Feb.
Rainfall is more frequent
驚蟄
Insects Waken
6th Mar.
Hibernating insects awaken
春分
Vernal Equinox
21st Mar.
Equal length of day and night
清明
Bright & Clear
5th Apr.
clear skies, fresh air, warm weather and lush plants
穀雨
Grain Rains
20th Apr.
Increased rainfall, which is beneficial to crops
立夏
Summer Commences
6th May
The beginning of Summer
小滿
Crop Forms
21st May
Crops are plump
芒種
Crop in Ear
6th Jun.
Beginning of the farming season
夏至
Summer Solstice
21st Jun.
Summer extreme
小暑
Moderate Heat
7th Jul.
Weather will be getting hotter and hotter
大暑
Great Heat
23rd Jul.
Supposed to be the hottest day of the year
立秋
Autumn Commences
8th Aug.
The beginning of Autumn
處暑
End of Heat
23rd Aug.
Hot season is finished
白露
White Dew
8th Sep.
Weather is getting colder and white dew can be seen
秋分
Autumn Equinox
23rd Sep.
Equal length of day and night
寒露
Cold Dew
8th Oct.
Dew will soon turn into frost
霜降
Frost
23rd Oct.
Weather begins to frost
立冬
Winter Commences
7th Nov.
The beginning of Winter
小雪
Light Snow
22nd Nov.
Snow starts falling
大雪
Heavy Snow
7th Dec.
Heavy snow every where
冬至
Winter Solstice
22nd Dec.
Cold starts to become unbearable
小寒
Moderate Cold
6th Jan.
Very cold weather
大寒
Severe Cold
20th Jan.
Supposed to be the coldest day of the year

1. Date can vary within a ±1 day range