Hi I'm Craig, up until now I thought it was Daylight Savings Time, not Daylight Saving Time and this is Mental_Floss on YouTube. Today I'm gonna answer Jerome's Big Question, why does Daylight Saving Time vary by country? [whispers] Still sounds weird to me. Let's get started.

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Countries started using Daylight Saving Time or DST or dst [pronounces it as a word] during World War I. To clarify, any time I say DST in this video, I'm referring to setting the clocks ahead in the summertime so the sun is out longer during the evening hours, then returning to what's known as Standard Time during the Autumn.

Germany was the first country to do this. They implemented it in order to save energy. The British adopted it shortly after, then most of the other countries in the war did, too. In the US, observing DST was a federal law for both of the World Wars, but after World War II it became a decision of the states.

Currently the majority of countries in North America and Europe observe Daylight Saving time. Most countries in Asia or Africa don't. Only about 70 countries or 1/4 or the world's population observe it. But a lot of countries have flip-flopped on DST over the years and probably will continue to. This is for a couple reasons.

Some people believe that it saves energy, some say that it's bad for health, and some think it's just an inconvenience. There's no clear consensus on whether Daylight Saving Time actually saves energy. In 2008, The National Bureau of Economic Research or NBER [pronounces it as a word] found that even though people use less light during DST, they use their air conditioning more, so there's actually an increase in energy. Oh geez. The US Department of Energy on the other hand claims that .02% less energy is used annually thanks to DST.

Experts also don't agree on whether it's a health issue. Come on, experts, can't we all get along! Can we? Do some research, you're experts, find out if we can. Some studies show that our bodies never adjust to DST and it increases the risk of illness. Others say that an extra hour of sunlight encourages people to be healthy and exercise more. That said, I can't go through and tell you why each country does or doesn't observe DST because I-- my own daylight is limited and I have to save it. But I can give you some examples.

In 2011 Russia declared that it would stay in DST year-round, but people hated it because of the dark winters, so they switched to standard time. Some predominantly Muslim countries like Morocco don't use DST during Ramadan because people fast during daylight, so they prefer the sun goes down earlier. Others just avoid DST altogether.

In the US, two states regularly don't observe DST: Arizona and Hawaii. Arizona because they're a bunch of jerks, Hawaii because they're an island off in the middle of nowhere and it doesn't matter. Noooo, Arizona you're probably great. You haven't observed it since the 60's. Officials believe they're saving energy by not having an extra hour of sunlight, time that people would likely spend running their air conditioning. And Hawaii's latitude makes it so that DST wouldn't affect them that much, they get basically the same amount of sunlight no matter what season and they're weather is perfect all year round have you been to Hawaii it's amazing!

Thanks for watching Mental_Floss on YouTube, made with the help of all of these nice daylight savers. If you have a big question of your own that you'd like answered, leave it below in the comments. See you next week.

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