First Day of Fall 2027

Southern Hemisphere

South of the equator the seasons are reversed, in Australia, New Zealand, South Africa and Argentina alike. In Sydney the September equinox occurs on Thursday, September 23, 2027 at 4:01 PM AEST. Australia's Bureau of Meteorology uses meteorological seasons, so in Australia spring is usually counted from September 1.

Why the first day of fall changes date

The calendar year has 365 or 366 days, but the tropical year — the time from one September equinox to the next — averages about 365.242 days, roughly 5 hours 49 minutes longer than a common year. So the September equinox comes about six hours later on the clock each year, and every leap day pulls it back by about 18 hours. Leap years therefore keep it within a two- or three-day window instead of drifting through the calendar. The Gregorian rule that skips leap days in century years not divisible by 400 (1900, 2100) keeps the window from creeping earlier over the centuries.

Change in clock time from one year to the next:

• 2026 → 2027: +5 h 56 min
• 2027 → 2028: −18 h 16 min (leap year)
• 2028 → 2029: +5 h 53 min

The year-to-year change is not exactly 5 h 49 min because the Moon and planets slightly perturb Earth's orbit.

The Sun and daylight on the September equinox

• The Sun crosses the celestial equator heading south and stands directly overhead at the equator at local noon. It rises close to due east and sets close to due west everywhere on Earth.
• Day and night are each close to 12 hours almost everywhere, with daylight a few minutes longer because of the Sun's apparent size and atmospheric refraction. At mid-northern latitudes the day with equal daylight and darkness comes a few days after the September equinox.
• From the September equinox to the March equinox, nights are longer than days in the Northern Hemisphere, and they keep lengthening until the December solstice.
• At the North Pole the Sun sets around the September equinox and stays below the horizon for about six months; at the South Pole it rises.

The full moon closest to the September equinox is the Harvest Moon; in 2027 it falls on Wednesday, September 15, 2027. See the 2027 full moon calendar.

In 2027, daylight saving time ends on Sunday, November 7, 2027, 45 days after the equinox.