The winter solstice in New Zealand is today. Here's how the shorter days of winter can affect your sleep patterns

RNZ News

20-06-2025

By
Georgie Hewson
, ABC
Photo:
Unsplash+
Australia and New Zealand will have their "shortest day of the year" today as the Southern Hemisphere experiences the winter solstice.
Where you are will determine just how much daylight you will get.
The shortest day of the year can also impact your sleep.
Here's what that means.
Saturday, 21 June.
According to
timeanddate.com
, the exact moment the Southern Hemisphere is at its furthest tilt from the Sun will be at 2.42 pm (NZT).
While the winter solstice is referred to as the shortest day and longest night of the year, it just means it is the day with the least amount of daylight hours.
That's because it's when the Southern Hemisphere is at its furthest tilt away from the Sun, meaning we get less sunlight.
At the same time, the Northern Hemisphere will be experiencing the summer solstice, which is the longest day of the year.
This happens because the Earth tilts at about 23 degrees, meaning that when one side is closest to the Sun, the other side is furthest away.
As the Earth does a lap around the Sun each year, different parts of the planet get more sunlight than others.
The Earth's slight tilt is what gives us our seasons.
Photo:
Supplied / Bureau of Meteorology, Australia
After Saturday, each day's total sunlight hours will get a fraction longer than the previous day until we reach the summer solstice on 22 December.
According to the astronomical definition of the seasons, the winter solstice in some places marks the beginning of winter.
But in Australia and New Zealand, where only meteorological seasons are observed, this is not the case.
That's why the beginning of winter is 1 June here.
In some cultures, the winter solstice is celebrated as a time of rebirth because the days get longer.
Because it is getting dark so early and the days are shorter, some people may experience changes in their sleep schedule and quality.
Elise McGlashan, from the University of Melbourne's John Trinder Sleep Laboratory, said shorter days and longer nights mean less sunlight, which can change circadian rhythms.
The circadian rhythm is the internal body clock that regulates sleep.
Photo:
AFP/Alexander Farnsworth
"Those changes in sleep can also be accompanied by changes in timings and function of our internal clock, and the function of our clock is mainly driven by environmental light exposure," she said.
"In summer, we know the sun might be up until it's close to someone's bedtime, and part of the reason people are sleeping a little longer is they aren't getting those light cues when they're trying to wind down.
"But during winter, there is less light and more time to wind down."
When there is less light exposure, the body produces more melatonin - a hormone that makes people feel sleepy - and less serotonin, which can lower mood and energy, leading to feeling tired or sluggish.
As the sun comes up later, it may be tempting to sleep longer, but oversleeping can also impact health.
McGlashan recommends getting outside for some sunlight during the day and letting sunlight into your bedroom in the mornings if possible.
"Our rhythms need bright days and dark nights," she said.
"It can be hard to motivate ourselves to go outside in winter, particularly in a really chilly location, but even on those overcast days, the light outside is going to be brighter than indoor lighting.
"It's still really helpful for your body clock and sleep to get outdoor lighting every day."
- ABC