Days will be shorter than nights in Australia in just over a week's time.

The autumnal equinox will occur at 7:37pm AEST next Saturday (March 20th), marking the moment the sun appears to be positioned directly above Earth’s equator. Following Saturday’s equinox, the sun will appear to move above the northern hemisphere as the south pole becomes tilted away from the sun.

Image: Visible satellite image taken on Friday March 12th, showing the solar terminator (line between day and night) running almost straight between the north and south poles. The solar terminator runs perpendicular to the equator at the equinox. Source: RAMMB/CIRA - Himawari-8

After the autumnal equinox, days become shorter than nights in Australia and the rest of the southern hemisphere. Nights outlast days for the next six months until the spring equinox in September. Australia's shortest day of the year occurs around the winter solstice, which takes place in late June.

While meteorological seasons are defined using full calendar months (autumn is March, April and May), some parts of the world use the solstices and equinoxes to mark the transition between seasons. 

Regardless of which definition you use, it's going to be autumn in Australia by next Sunday.