Earth Day is being commemorated on April 22. Held around the world, it’s intended as a moment to reflect on and help preserve the health of the planet – but here are five things that you might not have known about the annual event.

1. It’s going to be more important than ever this year

Earth Day is usually a moment to reflect on the importance of our environment and hopefully help change it for the better. But this year there’s going to be an important way of fixing our climate happening, at the same time.

As well as the normal events, Earth Day will will see the signing of the landmark Paris Agreement, which was agreed late last year. Though it has already been agreed, April 22 marks the day it will be signed and then brought into force.

The Paris Agreement contains within it many of the commitments that experts hope can fight some of the damage of climate change. It includes commitments to deal with greenhouse gases and to adapt to the changing world, all of which those behind it say will help move towards reducing global warming and keeping climate change below the thresholds that could lead it to wreak huge destruction upon the Earth.

2. Earth Day has its own flag

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John McConnell designed the Earth Day Flag using a NASA photograph of Earth (Wikipedia)

The Earth Day flag is fairly obvious: it’s an image of the planet (the famous "Blue Marble" picture that was taken by the Apollo 17 spacecraft as they travelled towards the Moon) placed on a dark blue background. It was created by John McConnell and has caught on perhaps because it is such a neat way of realizing what Earth is about: the entire planet, and its health.

3. Nobody really knows where the name came from

Earth Day might seem a fairly obvious name. And it’s for that reason that how it actually came about has been lost to time.

While a number of different names were suggesting during the build-up to the very first Earth Day—including the "National Environment Teach-In"—the name Earth Day stuck and has been used almost every year since.

Organizers say they aren’t really clear who came up with the name, because it was suggested by so many people and was so obvious that it just sort of came about, rather than being the work of any particular person.

4. And the date is just as meaningless, too

When Earth Day was first proposed, it was meant to happen on March 21, the beginning of Spring in the northern hemisphere. But then it didn’t.

Instead, organizers picked the date as a way of ensuring that as many students would be able to turn up as possible: in 1970, 22 April was a Wednesday, so it wouldn’t clash with other events; it didn’t clash with other big holidays, or exams;

5. Earth Day isn’t even its official name any more

In 2009, the UN decided that it would hold "InternationalMother Earth Day", and the first followed the year after. Since that agreement was endorsed by most of the UN’s member states, and it encourages the celebration of the day in all member states, that can be said to be the official name.

The UN added "Mother Earth" to the name because it "reflects the interdependence that exists among human beings, other living species and the planet we all inhabit", the UN said at the time.

The text also called the new era "the century of the rights of Mother Earth."