Lichun, Beginning of Spring, is the first of the twenty-four solar terms, jieqi, the documented division of the sun's ecliptic path into twenty-four fifteen-degree segments, Lichun arriving when the sun reaches 315 degrees, February 3rd to 5th in the Gregorian calendar. The BaZi tradition keys the year pillar to the solar terms, not the lunar calendar: the month pillars begin at the jieqi and the year at Lichun, so that a child born in late January 2017 is, by the documented rule, a Monkey, not a Rooster, the Lunar New Year that year falling January 28th. The folk calendar's own compromises are documented: the lunar new year governs the festival, the solar terms govern the agriculture and the astrology, two calendars doing two jobs, the marriage calendar, the farmers' almanac, and the chart all reading different clocks.
The folk consequence is the tradition's favorite correction: everyone born between January 1st and Lichun carries the previous year's animal in their chart, a fifth of the zodiac's customers reading the wrong placemat, and the practitioners' intake ritual, date, exact hour, city, exists precisely to fix the clock before the reading. The tradition's own note on the confusion: the two calendars were never meant to be fused, the solar terms being the farmers' and astrologers' clock, the lunar months being the festival's, and the modern zodiac industry merging them being the archive's favorite kind of error, a simplification that became the standard, the party date eating the solar date because parties are memorable and 315 degrees is not.
The claim: Lichun is the archive's favorite calendar lesson, the real beginning arriving unannounced, the sun crossing a degree line with no festival, while the celebrated beginning is the lunar one, scheduled for the crowd, so that the calendar itself teaches the archive's standing doctrine: the operative event and the announced event are rarely the same, and the one with the fireworks is for the year pillar's public face, not for the farmers or the charts. Verdict: the archive files the two new years as the calendar's own four-pillar structure: the festival is the public face, Lichun is the day master. The tradition has run both clocks for two millennia without confusion, the confusion being a documented feature of the export version. The year turned, per the solar terms, on February 4th. The party, per the moon, came later. The archive notes which one the fields obeyed. Check which one you were born under. The placemat, per the tradition, may be the previous year's.
If the astrological year begins three weeks before the celebration, which new year is the real one, and why does the real one have no party?