Summer Solstice夏至

Summer Solstice (夏至, Xià Zhì) is the tenth of the twenty-four solar terms and the point where the sun reaches its highest path of the year. It is an astronomical instant, not a day: the moment the sun reaches 90° of ecliptic longitude, which falls on 21 or 22 June depending on the year — the day with the most daylight of any in the calendar.

It is also the term most likely to be assumed to open something in a chart, because it is famous outside BaZi as a turning point in its own right — the peak of the sun's northern path, mirrored six months later by the Winter Solstice at the bottom. Inside BaZi it carries none of that structural weight: it is a mid-month marker, not a month-opener.

It falls at the midpoint of the 午 month that Grain in Ear opened roughly two weeks earlier, and it is followed roughly two weeks later by the next 節, Minor Heat. Its place in the agricultural calendar is exactly what the astronomy says: the sun's highest point, the day's peak length, and the turn after which daylight begins, very slowly, to shorten again.

Summer Solstice is a 氣 — a mid-month term — and a 氣 changes no pillar at all. The month pillar's branch was already set to 午 when Grain in Ear opened this month, and it stays 午 straight through to the next 節, Minor Heat. A birth at the Summer Solstice and a birth a week before or after it can carry the same month pillar with nothing about the solstice itself moving it.

This site's calculator treats every 氣, this one included, as a marker with no effect on the four pillars: it is useful for describing where in the solar year a birth falls, but the year, month, day and hour pillars are computed from the 節 boundaries and the calendar, not from the solstice.