The Southern Hemisphere Is in Spring While We Just Hit the Autumn Equinox: The Boundary Between Solar Terms and the Month Order

At one in the morning a calendar alert popped up on my phone: "Autumn Equinox today." I flipped over to the date in Brazil — it read 21:05 on 22 September, the first minute of spring.

The same day, two calendars, two seasons.

Nobody wrote it down wrong. The 2026 Autumn Equinox falls at 08:04:56 on 23 September (about 08:05, China Standard Time); the same instant converted into Brasília time is 21:05 on 22 September. At that very moment the northern hemisphere entered autumn and the southern hemisphere entered spring. The Chinese-language calendar records the 23rd, the press release from Brazil's National Observatory gives the 22nd — both are right.

Solar Terms Measure the Sun, Not the Temperature

On the character fen that gives the autumn and spring equinoxes their Chinese names, Wu Cheng of the Yuan dynasty was at his most economical in the Monthly Ordinances and the Seventy-Two Seasonal Indicators Explained (Yueling Qishi'er Hou Jijie): the Autumn Equinox entry is just one line, "Autumn Equinox: mid-eighth month. For the explanation, see the Spring Equinox" — which means that to read the Autumn Equinox you have to turn back to the Spring Equinox entry:

Fen means half. This marks the midpoint of the ninety days, and so it is called the divide. Autumn carries the same meaning.

Fen means "half": a season runs ninety days, and the forty-fifth day is exactly the halfway point. What it measures is where the sun stands on the ecliptic, and it has nothing to do with temperature. That is precisely why this calendar holds for both hemispheres equally — what it divides is the sun, not the weather.

What is genuinely tied to a region is the next step: the month order (yueling).

Why the Month Order "Doesn't Line Up"

BaZi takes the month order as its framework: the yin month is the first month, running from the Start of Spring to Awakening of Insects; the mao month is the second month, from Awakening of Insects to Clear and Bright. The month establishment (yuejian) follows the solar terms, the solar terms follow the sun, and there is no problem with that.

The problem lies in what a season means. The names in the "yin month" set carry the phenology of the northern hemisphere: around the Start of Spring the ice and snow begin to melt, and after Awakening of Insects the insects stir and the grass grows. At that same time the southern hemisphere is in late autumn — so anyone born in the southern hemisphere takes one look at the chart and feels that the seasons don't line up.

This is not the system going wrong; it is a question of the range over which it applies. It is the same class of thing as "eating dumplings at the winter solstice": a body of seasonal experience that grew out of one particular region, written up as universal names.

Three Things to Confirm Before Casting a Chart in the Southern Hemisphere

1. The longitude of your birthplace. The clock time on the record first has to be converted into local true solar time; this one matters just as much in either hemisphere.
2. That year's time zone and daylight saving. In some years and some places the clocks have been moved, and moving the clock genuinely affects which two-hour period (shichen) a moment belongs to.
3. The actual local season, as a common-sense cross-check. Once true solar time is fixed and the month order has been laid out, hold it against the local weather and phenology for that month — if they don't match, ask why, and the answer usually comes out of the time zone or the longitude.

As for whether to use the month order "upside down," practice is not unified: some people re-read strength and weakness according to the local season, while others keep to the four pillars' own system of symbols and merely explain the difference when interpreting. Both approaches have their users, and what separates them is how you state your own terms — which is also why, when I read the BaZi Basics: Four Pillars, Ten Gods, Patterns and the Useful Element, the section I look at first is the one on how the useful element is determined: the month order is the starting point for judging strength and weakness, and if the starting point is off, everything after it is off too.

Can This Calendar Still Be Used, Then?

Yes. Treat it as a northern-hemisphere phenology table measured by the sun: the moments of the solar terms are the same the world over, while their names carry a region with them. If you are in the southern hemisphere you can read it against the local season — our autumn equinox, for instance, corresponds to the phenology around the local spring equinox.

Later I sent my friend in São Paulo a photo — here the wind chimes on the balcony were ringing in the wind, and the yellow flowers at her flower stall had already sold out. The same minute, two seasons, and neither of us was wrong.

If you are not sure how your own birth time should be converted either, then on 占卜迷指 it works like this: you describe your trouble in natural language, the system recommends a suitable method, casts the chart and gives a reading, and you can export it to keep and compare against slowly. And if you would rather understand first how solar terms hook onto the "suitable" and "avoid" lines, see Huangli Date Selection: Where the Suitable and Avoid Lines Come From.

Information current as of 23 September 2026 (China Standard Time).

Sources

• Brazil's National Observatory (Observatório Nacional do Brasil): Primavera 2026 começa no dia 22 de setembro — the southern hemisphere's spring equinox at 21:05 on 22 September (Brasília time), with spring lasting until 21 December
• CNN Brasil (2026-09): Primavera 2026: the seasonal forecast and what an equinox is — the equinox moment at 21:05 on 22 September (Brasília time)
• Autumn Equinox 2026 time lookup (jieqi.bmcx.com) — the Autumn Equinox on 23 September 2026 at 08:04:56 (Beijing time)
• Monthly Ordinances and the Seventy-Two Seasonal Indicators Explained (Yueling Qishi'er Hou Jijie), Wu Cheng, Yuan dynasty, Wikisource — the Autumn Equinox entry reads "mid-eighth month, for the explanation see the Spring Equinox"; "Fen means half; this marks the midpoint of the ninety days, and so it is called the divide" appears in the Spring Equinox entry

(Note: the seasonal table page of Brazil's National Institute of Meteorology, INMET, is unreachable from the current network environment; this page is therefore not cited; the seasonal timings come from the reachable National Observatory of Brazil and CNN Brasil.)

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