Daylight Saving Time 101 | National Geographic

Daylight saving time adds extra hours of daylight during the summer season while making the day shorter during the winter months. But who came up with the concept of daylight saving time, and how does it work?

The concept of shifting our clocks to adjust the length of the day can be traced back to over 100 years ago. In 1895, New Zealand entomologist George Hudson made the earliest known proposal for a time shift, submitted to the Wellington Philosophical Society. The idea was well-received, but it didn't catch on.

In 1905, British builder William Willett developed a similar idea independently of Hudson. He lobbied the British Parliament year after year to no avail until his death in 1915. The issue was revisited time and again throughout the world, but it wasn't officially put into practice nationwide until the early 20th century.

In Germany, the Germans, in the throes of World War One, were looking for ways to conserve energy. They decided that more daylight was the answer and became the first country to enact daylight saving time. Today about 70 countries around the world practise daylight saving time.

Clocks in the northern hemisphere are usually set ahead by one hour toward the end of March or early April. In late September or early October, they're set back one hour. In the southern hemisphere, the reverse occurs.

While many countries originally adopted daylight saving time to extend daylight hours and cut down on the need for artificial light, critics today say it no longer saves energy. In fact, an estimated 80 percent of the global population does not use daylight saving time.

Some countries are divided about its use. In Australia, three out of eight states and territories do not practice daylight saving time. In the United States, Hawaii and most of Arizona do not bother with daylight saving time, and some states are considering doing away with it.

There are also apparent health and safety issues that come into play. The shift to and from daylight saving time has been linked to an increased risk in heart attacks and automobile fatalities.

There's no shortage of opinion when it comes to daylight saving time, and whether the world will agree on how to manage our clocks is yet to be seen.

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