Beginning of Autumn立秋

Beginning of Autumn (立秋, Lì Qiū) is the thirteenth of the twenty-four solar terms and the first of the three autumn month-openers. It is an astronomical instant, not a day: the moment the sun reaches 135° of ecliptic longitude, which falls on 7 or 8 August depending on the year — while Major Heat's hottest stretch is still fresh in memory.

Like Beginning of Spring, 立 here means "to set up" or "to establish" rather than "to arrive": the term declares autumn rather than delivering it. Early August in most of the northern hemisphere is still deep summer by any thermometer, and the cooling the name promises is still weeks away.

Astronomically it sits at the midpoint between the Summer Solstice and the Autumn Equinox, making it a cross-quarter term — the same structure that produces Beginning of Spring, Beginning of Summer and Beginning of Winter at the other three cross-quarter points. In the agricultural calendar it marks a turn in the farming year's second half: the point after which planning shifts from growth to the coming harvest, even as the hottest days themselves have not yet let go.

Beginning of Autumn is a 節 — a month-opening term — so at the instant the sun crosses 135° the month pillar's branch becomes 申 (Shēn). This is the term that puts 申 in place for anyone born from this instant forward until the next 節, End of Heat's successor White Dew, arrives roughly a month later.

This site's calculator applies that rule at the astronomical instant, not on a fixed calendar date: a birth in the days around 7–8 August can carry either 未 (from Minor Heat, the previous 節) or 申, depending on which side of the crossing the birth time falls.