Australia is about to pass an annual daylight milestone, with days set to become longer than nights across the country as the spring equinox approaches.

What is the equinox?

Earth’s orientation relative to the Sun changes throughout the year because Earth has an axial tilt of about 23.4 degrees relative to its orbital plane around the Sun.

Earth’s axial tilt means that Earth's Northern Hemisphere is tilted more towards the Sun for half the year, while the Southern Hemisphere becomes more tilted towards the Sun during the other half of the year. This changing orientation relative to the Sun is what causes our seasons.

The summer and winter solstices, which happen in December and June, mark the dates on which each hemisphere reaches its furthest tilt towards and away from the Sun. In between these two dates are the equinoxes – in March and September – when Earth’s axial tilt is oriented neither toward nor away from the Sun.

The Sun appears to sit directly above Earth’s equator on the date of the equinox, which causes roughly equal lengths of day and night for most of the planet.

Image: Approximate sunrise, sunset and day length times on the date of the Southern Hemisphere’s spring equinox in 2026. Source: Weatherzone.

Day and night not exactly equal on the equinox

While day and night are almost equal in length on the date of the equinox, they aren’t quite the same. There is a bit more daylight than darkness on the equinox for two main reasons:

Sunrise and sunset are defined as the moment the top edge of the Sun reaches Earth’s horizon. Because the Sun’s face appears as a large disc and not a single point, it takes several minutes for the full face of the Sun to rise and set. This adds a bit of extra daylight at either end of the day. If sunrise and sunset were defined as the moment when the centre of the Sun reached the horizon, then day and night would be closer to equal length on the date of the equinox.

Earth’s atmosphere bends light. This means sunlight is visible even when the Sun is just below the horizon, which helps make the day longer in terms of light.

Night and day are closer in length a few days before the equinox. This date, which varies depending on latitude, is called the equilux.

The 2026 spring equilux will occur this weekend in Sydney and Melbourne, with Saturday having the closest amount of time for day and night in Sydney and Sunday for Melbourne.

Days will start getting longer than nights across Australia following the equilux, and this trend will continue for the next three months until the summer solstice in late December.