Born on a Solar Term Day: Your BaZi Month Comes Down to the Minute

A BaZi month is neither a Gregorian month nor a lunar month but a solar-term month: from the Start of Spring to the Awakening of Insects is the Yin month, from the Awakening of Insects to Pure Brightness the Mao month, and so on. The line between months is the moment a jie term arrives, to the minute. Two people born on the same day, one before the term and one after, have different month pillars.

Three rules

• The year pillar changes at the Start of Spring (Li Chun, 立春): not on the first day of the lunar year and not on January 1. The Start of Spring usually falls on February 3, 4 or 5.
• The month pillar changes at a jie (節) term: the twenty-four solar terms divide into twelve jie and twelve zhong qi (中氣, middle terms). Only the jie change the month: Start of Spring, Awakening of Insects, Pure Brightness, Start of Summer, Grain in Ear, Minor Heat, Start of Autumn, White Dew, Cold Dew, Start of Winter, Major Snow and Minor Cold.
• The exact moment is what counts: a solar term is an astronomical event and happens at the same instant everywhere. To compare, both times must be on the same clock; we use UTC+8, and the tool converts births abroad automatically.

The twelve jie terms in 2027 (UTC+8)

Calculated with our calendar engine (lunar-javascript). Taiwan, Hong Kong, China, Singapore and Malaysia all use UTC+8 today; elsewhere, convert. The Start of Spring is also when the Ding Wei year begins; see 2027 Ding Wei year.

The blind spot in ordinary forms: choosing an hour

Most chart forms, ours on the home page included, let you choose a two-hour period rather than a time. The program then compares a representative moment in that period (we use its midpoint) with the solar term. If the term happens to change inside the two hours you were born in, the form can get it wrong.

How we counted: our engine drew random birth times (to the minute) within each period, 12,000 per group, and compared the four pillars cast straight from the clock hour with the exact, corrected pillars. The modern Taiwan group was born 1980–2010; the daylight-saving group, 1946–1979.

The share is tiny, but for anyone who falls in it the whole year or month pillar is wrong, and the start and direction of the luck pillars go wrong with it. If you were born around the 4th to 8th of a month, check whether a term changed that day; the safest approach is to compare to the minute with the tool on this page.

Born on a term day: what else to check

• Daylight saving time: take it off before comparing with the solar term time. In Taiwan, term days in the summers of 1975 and 1979 both need an hour subtracted first.
• Born abroad: convert to the same clock before comparing; do not compare local clock time with a UTC+8 solar term table directly.
• Luck pillar starting age: the age at which luck pillars begin is worked out from the distance between birth and the nearest jie term. Someone born on a term day starts either very early or very late, which is normal; see starting age of the luck pillars.