Lichun (立春, "start of spring") is the solar term around February 4th that marks the true year boundary in BaZi (Four Pillars) astrology -- not Lunar New Year, which is a full lunar cycle and up to several weeks off from the astronomically correct cutoff.
The Chinese calendar actually runs two systems at once: a lunar calendar (used for Lunar New Year, festivals, and everyday dates) and a solar term calendar of 24 jieqi (节气) tied to the sun's position, independent of the moon. Lichun is the first of these 24 solar terms and falls close to February 4th every year, with only a day or two of variation.
Popular "what's your Chinese zodiac animal" tools almost universally use Lunar New Year as the year cutoff, because it's simpler and more widely known. But BaZi (Four Pillars of Destiny), the classical Chinese astrology system that reads your birth moment as four stem-branch pillars (year, month, day, hour), has always used Lichun as its year boundary -- a distinction that matters most for anyone born between Lichun and the following Lunar New Year, a multi-week window where the two conventions disagree on which year you belong to.
This isn't a stylistic choice or a modern reinterpretation -- it reflects BaZi's origins as a solar-term-based system for describing seasonal Five Element energy, which lunar months don't track consistently (a lunar year can start anywhere from mid-January to mid-February depending on leap-month placement). AstroKarmas uses Lichun for BaZi year-pillar calculation specifically, and documents this choice on the About & Methodology page since it's one of the more common places free astrology tools get the underlying math wrong.
The month pillar boundaries in BaZi follow the same solar-term logic -- each of the 12 BaZi months starts at a specific jieqi, not at the lunar new-moon month boundary most calendars show.
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