The Spring Equinox 2019 will be at 5:50 pm AEST on Monday 23 September.

This is when we have equal lengths of day and night.

Of course if you are in the Northern hemisphere it will be the vernal Equinox. And the start of autumn or fall.

So what is an Equinox? The equinox is generally accepted as occurring at the instant of time when the plane of Earth’s equator passes through the centre of the Sun.

This occurs twice each year: around March 20 and September 23. In other words, it is the moment at which the centre of the visible Sun is directly above the Equator.

In the northern hemisphere, it is commonly understood that the first day of Spring, Summer, Autumn and Winter occur with the relevant equinox (for Spring and Autumn) or solstice (for Summer and Winter). However in Australia and New Zealand it is conventional to say that each season begins on the 1st day of a month so Spring started on Sept 1. Of course the weather rarely follows either convention.

However, what is consistent across the countries is that the increase in the length of daylight each day reaches a peak at Spring Equinox when daylight and night are of equal length.