In a couple of weeks, Australia's three time zones will become five as daylight saving time kicks in.
This means it will be brighter later, especially in southern parts of Australia. At the height of the Hobart summer, for instance, the sun doesn't set until nearly 9pm.
And this "longer day" was why daylight saving time was introduced — not just here, but around the world.
It was, in essence, a way to save fuel during World War I.
With more "usable" hours of daylight, people didn't have to use as much fuel to light up homes and businesses.
But that was more than a century ago. Does the "saving" part of daylight saving time still hold up today?
Daylight saving time's rocky start
Daylight saving time may have its roots in World War I, but the seed was planted decades earlier.
In the 1890s, New Zealand post office worker and amateur entomologist George Hudson was the first to seriously propose shifting clocks forward during summer.
One of the benefits, he wrote, was "a long period of daylight leisure would be made available in the evening for cricket, gardening, cycling, or any other outdoor pursuit desired".
But when it was first floated, his idea received mixed reviews.
Some of his peers liked it; others said it was "wholly unscientific and impractical".
So not a whole lot happened with daylight saving time until the first world war broke out.
In 1916, Germany and Austria-Hungary became the first to introduce it across the board, and others around the world soon followed suit, including Australia.
We implemented daylight saving time across the nation during the summer of 1916-17, and again during the first couple of years of World War II.
These days, Australian states and territories decide if they want to observe daylight saving time, with Tasmania, Victoria, the Australian Capital Territory, New South Wales and South Australia having adopted it since 1971.
But only since 2008 have these states and territories started and finished on the same date: the first Sunday in October and first Sunday in April respectively.
And in recent years, it's becoming clear that the onset of daylight saving time — which disrupts our body clock, or circadian rhythm, when we have to get up an hour earlier — has some potentially profound health-related repercussions, like more heart attacks and depression.
So ... what about power savings?
The answer to this question depends on where you are and who you ask. Researchers around the world have come to varying and opposite conclusions.
Fortunately, there are a handful of studies specific to Australia, but unfortunately, and the short answer is: no.
Daylight saving time does not mean lower electricity usage overall for us.
But there's more to it than that.
A handy little natural experiment took place fairly recently in Western Australia, which has dipped in and out of daylight saving time since the 1970s.
Virginie Masson, an economist at the University of Adelaide, and a couple of colleagues analysed power usage over the course of the day during Western Australia's most recent stint of daylight saving time — 2006 to 2009.
Compared to a (non-pandemic) period with year-round standard time, they found daylight saving time resulted in no overall energy savings.
But what did shift was when people used electricity.
During standard time, there would usually be a large spike in energy use that coincided with people returning from work in the late afternoon and early evening.
Daylight saving time flattened that spike a bit. The peak wasn't as big, but it spanned a longer period, Dr Masson says.
The researchers also saw a slight uptick in morning electricity use during daylight saving time.
Dr Masson isn't sure why that was the case, but suspects that it might be people putting their heater on when they get up — especially at the start and end of daylight saving time, when the mornings are cooler.
"And so when you put the two effects together, the decrease in demand in the 4.30 to 8.30pm window is completely cancelled by the little increase in the mornings and later at night."
Still, there may be an energy benefit to daylight saving time, she adds: "Because of this smoothing of distribution, you avoid the very strong peak, which means you may avoid outages.
A similar conclusion was reached by a pair of American economists in 2007, who analysed power usage during another natural Australian experiment: the 2000 Sydney Olympics.
That year, daylight saving time in the south-eastern states was moved up to August 27.
When the economists compared the extended daylight saving period with previous years, they found daylight saving time reduced electricity demand in the evening, but had the opposite effect in the morning.
That spike first thing probably cost more, too, they wrote in their paper.
"Furthermore, the morning peak demand caused by Australia’s 2000 extension is associated with significantly higher wholesale electricity prices, indicating that the steep morning ramp-up in demand likely caused an increase in generation costs."
What Australia can teach the world
While the adoption of daylight saving time has remained pretty stable in Australian states and territories over the past decade or so, Europe is about to embark on a daylight saving reckoning.
In 2019, the European Union voted to abolish union-wide daylight saving, saying nations could decide if they want to keep it or not from 2021.
The pandemic temporarily put a pin in that, but 27 countries will need to make that choice in the coming year.
If electricity consumption is a factor in their decision-making process, research from Australia may help.
Cahit Guven, an economist at Deakin University, was part of a team that analysed Australian electricity usage data and daily weather conditions from 1998 to 2015.
They found any energy-saving benefits of daylight saving time boil down to the weather and air conditioner ownership.
Air conditioners are why the "saving" part of daylight saving time no longer holds true in many warm parts of the world.
When daylight saving time was first introduced, most household energy during summer went to keeping rooms lit.
Now the lion's share goes to the electricity-hungry air conditioner, more than offsetting any lighting-related savings.
"We found we can explain all the previous literature — that electricity consumption [during daylight saving time] declines in a place where the temperatures are low and air conditioner usage is low," Dr Guven says.
In their paper, published in June, Dr Guven and his colleagues ran simulations for European countries to find out which ones save electricity during daylight saving time.
With current conditions and air conditioner ownership, countries such as Greece and Cyprus should do away with daylight saving time.
Germany, on the other hand, might benefit by sticking with it.
"We set out the formula, so each country or state can put their own values of air conditioner ownership and temperature in our equation, and they can see the impact of daylight savings adoption," Dr Guven says.
What could change the game for parts of Australia that adopt daylight saving time — even the warmer parts with lots of air conditioners — is wider uptake of rooftop solar power.
"If in the future, let's say that 90 per cent of houses use solar power," Dr Guven says.
"In that case, [air conditioner use during daylight saving time] might not be a big problem, because even though it is really hot, you're creating your own electricity.
"So you might be actually better off."
