Autumn is right around the corner for everyone in the Northern Hemisphere, while those in the Southern Hemisphere are gearing up for warmer spring weather.

On Sept. 22 at 9:54 p.m. EDT (0154 GMT on Sept. 23), the sun will cross the celestial equator, or an imaginary line that projects Earth’s equator into space. At this exact moment, the Northern and Southern hemispheres will receive an equal amount of sunshine, and the length of day and night will be approximately equal around the world — hence the term “equinox,” which is derived from the Latin phrase meaning “equal night.”[…]

Source: Why the Autumnal Equinox Doesn’t Fall on the Same Day Every Year