24 Solar Terms (二十四节气)

The 24 solar terms were created by astrologer in ancient China based on the sun's position in the zodiac to guide the seasonal agriculture activities. During the Warring State period 戰國時代 (475BC to 221BC) only 8 main solar terms were created to mark the four seasons.

By the time of Western Han Dynasty 西汉 (206BC - 24AD), it was further improved by the creation of another 16 sub-solar terms to reflect more accurately the seasonal changes in climate and weather. Total solar terms became 24.

Since the timing of the 24 solar terms were based on the sun's movement, the date for the starting of each solar term can be quite accurately stated by solar calendar or Gregorian calendar with variation of 1 day.

But the dates of the 24 solar terms in a lunar calendar can vary by up to 30 days.

Lunar Calendar

A lunar calendar is based on cycles of the lunar phases as the moon orbits around the earth.

The absolute period taken by the moon to complete one orbit is 27.32 days. But, while the moon is orbiting the earth, the earth-moon system is orbiting the sun at the same time.

For an observer on earth, the period taken by the moon to return to the same apparent position with respect to the sun is 29.53 days. Thus each month of the lunar calendar has either 29 days or 30 days. A lunar year with 12 months has only 354 days, that is 11 days shorter than a solar year of 365 days. To adjust this difference of 11 days a year, ancient Chinese added one extra month to every third lunar year. This 2017 rooster year is the third lunar year, so it has 13 months. The extra month is on the 6th month. There will be two 6th month in 2017 lunar calendar.

Li Chun (立春)

Li Chun is the first solar term and the starting of Li Chun marks the starting of spring. In ancient China, the emperor would conduct an elaborate ceremony on Li Chun to declare and to celebrate the starting of a new year.

The 2016 'Monkey' year was from 8th February 2016 (after the 4th February 2016 Li Chun) to 27th January 2017 (before the 3rd February 2017 Li Chun), thus there was no LI Chun throughout the whole 'Monkey' year. The year was termed a 'Blind Year' (盲年), a year without Li Chun.

Came this 2017 Chinese New Year on 28th January 2017 with its first Li Chun on 3rd February 2017. Because this lunar year has 13 months, it will end on 15th February 2018 after the 2nd Li Chun on 4th February. With 2 Li Chuns within a year, this Rooster year is termed 'Shuang Chun Nian' (双春年). A year that is good for marriage.

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