The beginning of spring

立春 (lì chūn, start of spring) signifies the beginning of spring in China, Japan and many other Asian countries, where spring equinox would be the middle of the season.

Spring begins when the Sun reaches the celestial longitude of 315 degrees, which occurred at 2007-02-04 05:18 UTC this year.

Spring could be divided into 3 equal parts. The first part is 孟春 (mèng chūn, early spring), the second part is 仲春 (zhòng chūn, middle spring), and the last part is 季春 (jì chūn, late spring).

Each of the 3 parts could be divided into 2 solar terms (節氣, jié qì):

• The first half of 孟春 is 立春 (lì chūn) and the second half is 雨水 (yǔ shuǐ)
• The first half of 仲春 is 驚蟄 (jīng zhé) and the second half is 春分 (chūn fēn, spring equinox)
• The first half of 季春 is 清明 (qīng míng) and the second half is 穀雨 (gǔ yǔ)

Each of terms could be divided into 3 pentads (候, hòu). So there are 18 pentads in spring, and 72 pentads in a year. Each pentad has a name, for example, the first pentad in spring from roughly February 4 to February 8 in the Gregorian calendar named 東風解凍 (dōng fēng jiě dòng).