Lichun vs Chinese New Year: two ways the zodiac year begins

The Chinese calendar keeps two kinds of time at once. Lunar months begin on the day of each new moon, and the year they make starts on Chinese New Year. Alongside them run the 24 solar terms, which follow the Sun; the first of them, Lichun (立春, Start of Spring), marks the solar start of the year. Because one follows the Moon and the other the Sun, they rarely fall on the same day.

For the zodiac this matters. Under the popular rule the animal changes on Chinese New Year. Under the Four Pillars rule it changes at the moment of Lichun. A birthday between the two dates gets a different animal depending on the rule.

Which comes first

From 1901 to 2100, Lichun comes before Chinese New Year in 103 years and after it in 91. They fall on the same day in only 6 years: 1905, 1924, 1943, 1992, 2038 and 2087. Even then the two rules differ for a few hours, because Lichun happens at a set time on that day.

Why Lichun is February 3, 4 or 5

Lichun is the moment the Sun reaches 315 degrees of ecliptic longitude. The Gregorian calendar keeps that moment close to the same date, but its leap-year pattern moves it by about six hours a year and then back. Over the long run the date drifts earlier, because the Gregorian year is slightly longer than the solar year: February 3 never occurred between 1901 and 2016, and it becomes common from 2017.

Double-spring and blind years

A 12-month lunar year has 353 to 355 days, shorter than the solar year, so it can start just after one Lichun and end just before the next: such a year contains no Lichun and folk custom calls it a blind year (盲年). A 13-month year, with a leap month, runs about 384 days and can contain two, one near each end: a double-spring year (双春).

From 1901 to 2099 there are 73 double-spring years and 73 blind years (the 2100 lunar year ends in 2101, past the Observatory tables, so it is left out). Every double-spring year in that range is a year with a leap month, and every leap-month year is a double-spring year. These are calendar facts; the customs attached to them are folk beliefs, not rules of the calendar. See Chinese leap months for how the 13th month is added.