Traditional Chinese Calendar

Zeus Sensor uses the Traditional Chinese Calendar as the base for its calculations. This calendar is different than the Gregorian (Western) calendar because it is influenced by both the moon and the sun, technically called a "Lunisolar" calendar. Without getting too deep into the inner workings of the calendar, the following is a brief introduction to its main concepts and why it is used.

12 Lunar Months

A lunar year has 12 lunar months or cycles. A complete lunar cycle begins with a new moon (fully dark) to a full moon in the middle of the cycle, the moon then wanes towards the next new moon to start the next cycle. Each cycle takes about 29.5 days to complete. The first day of the lunar year begins with the first new moon of the first lunar month, which typically takes place between January 21 and February 20 in the Western Calendar. The 12 lunar months, however, do not precisely align with the 365 days of the solar year (29.5 x 12 = 354 days), therefore the Chinese developed a system of leap months to maintain balance. Within a 19 year period, there will be 7 years that will include an extra month.

24 Solar Terms

The Chinese use something called the Farming Calendar to help regulate agricultural activities throughout the year. This calendar dates back more than 4,000 years and is still in use today. The year contains the 4 seasons, with 6 sub-seasons each to give a total of 24 Solar Terms. These terms indicate the changes in temperature and weather conditions so that the farmers of rural China can plan the dates for ploughing, planting, harvesting, etc. The first solar term is called the Beginning Of Spring.

The 24 Solar Terms of the Chinese Farming Calendar

Chinese Pinyin	Chinese Name	Approximate Gregorian Date	English Name	Month Name	Five Elements
Li Chun	立春	February 4	Beginning of Spring	Tiger; First	Yang Wood
Yu Shui	雨水	February 19	Rain Water
Jing Zhe	惊蛰	March 6	Waking of Insects	Rabbit; Apricot	Yin Wood
Chun Fen	春分	March 21	Spring Equinox
Qing Ming	清明	April 5	Pure Brightness	Dragon; Peach	Yang Earth
Gu Yu	谷雨	April 20	Grain Rain
Li Xia	立夏	May 6	Beginning of Summer	Snake; Plum	Yin Fire
Xiao Man	小满	May 21	Grain Full
Mang Zhong	芒种	June 6	Grain in Ear	Horse; Guava or Pomegranate	Yang Fire
Xia Zhi	夏至	June 22	Summer Solstice
Xiao Shu	小暑	July 7	Lesser Heat	Sheep; Lotus	Yin Earth
Da Shu	大暑	July 23	Greater Heat
Li Qiu	立秋	August 8	Beginning of Autumn	Monkey; Orchid	Yang Metal
Chu Shu	处暑	August 23	End of Heat
Bai Lu	白露	September 8	White Dew	Chicken; Osmanthus	Yin Metal
Qiu Fen	秋分	September 23	Autumn Equinox
Han Lu	寒露	October 8	Cold dew	Dog; Chrysanthemum	Yang Earth
Shuang Jiang	霜降	October 24	Descent of Frost
Li Dong	立冬	November 8	Beginning of Winter	Pig; Good	Yin Water
Xiao Xue	小雪	November 22	Lesser Snow
Da Xue	大雪	December 7	Greater Snow	Rat; Winter	Yang Water
Dong Zhi	冬至	December 22	Winter Solstice
Xiao Han	小寒	January 6	Lesser Cold	Ox; Last	Yin Earth
Da Han	大寒	January 20	Greater Cold

Modern day use

Together, these lunar and solar concepts form the Traditional Chinese Calendar. Today it is still used in Chinese culture (and many other Asian cultures) to indicate the dates of national holidays and festivals. Because the ancients used this calendar during the development of Eastern astrology, therefore we adhere to the same practice with Zeus Sensor today.