September equinox
（重定向自Southward equinox）
![Illumination of Earth by Sun on the day of an equinox](/Images/godic/202502/12/Earth-lighting-equinox_EN3457.png")
The September equinox (or Southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Due to differences between the calendar year and the tropical year, the September equinox can occur at any time from the 21st to the 24th day of September.