The eclipse is coming. Next week, the moon will go in front of the sun and blot it out, turning the US dark.

It's the first time that such an event has been seen across the entire US for 99 years. And it will be the biggest ever movement of tourists the world has ever seen.

It's all leading up to that couple of minutes when the sun disappears. And, thankfully, we know exactly when that will happen.

What day is the eclipse?

It will all happen on 21 August, in the morning and early afternoon.

What time is the eclipse?

It lasts between mid-morning and mid-afternoon, depending where you are. It spreads from the west to the east, meaning that despite the fact it won't take long to actually cross the country, the timings make it look like it lasts much longer.

Partial Lunar Eclipse 2017 Show all 12 1 /12 Partial Lunar Eclipse 2017 Partial Lunar Eclipse 2017 A man takes pictures of the moon standing in a partial lunar eclipse on August 7 AFP/Getty Images Partial Lunar Eclipse 2017 The moon standing in a partial lunar eclipse hangs in the sky over Bad Staffelstein, southern Germany AFP/Getty Images Partial Lunar Eclipse 2017 PUT IN SOME TEXT The moon standing in a partial lunar eclipse can be seen behind a constructin crane on August 7, 2017 in Gilching, southern Germany AFP/Getty Images Partial Lunar Eclipse 2017 A man frames with his hands the moon standing in a partial lunar eclipse on August 7, 2017 in Frankfurt am Main, western Germany AFP/Getty Images Partial Lunar Eclipse 2017 A picture shows the moon during a partial lunar eclipse as seen from Kuwait City AFP/Getty Images Partial Lunar Eclipse 2017 Picture taken with long exposure time shows the rising full moon during a partial lunar eclipse (right side) over Frankfurt, Germany AP Partial Lunar Eclipse 2017 The rising moon is seen during a partial lunar eclipse behind the chimney stacks of an electric power station in Delimara, outside the village of Marsaxlokk, Malta REUTERS Partial Lunar Eclipse 2017 The full moon is seen during a partial lunar eclipse in Dresden, Saxony, Germany EPA Partial Lunar Eclipse 2017 This photograph shows a partial Lunar eclipse as seen from the southern Indian city of Chennai AFP/Getty Images Partial Lunar Eclipse 2017 The moon rises with the earth casting a shadow on it behind a construction crane during a partial lunar eclipse in Vienna, Austria REUTERS Partial Lunar Eclipse 2017 The August full moon rises above the 5th Century BC Temple of Poseidon at Cape Sounio, south of Athens AP Partial Lunar Eclipse 2017 People admire the full moon as it rises over the cape Sounio, 65 km south of Athens, Greece EPA

Obviously, exactly what time the eclipse arrives will depend partly on where you are. But as a rough guide, if you use pacific time then it will arrive at about 10.20 in the morning; if you use mountain time then it will be between 11.30 and midday; if you're on central time then it will arrive sometime between 1pm and 1.30; and those on the east coast will get it sometime between 2.30 and 3.

See below for exact details on when it will get to you, and how it will move across the country.

How long will it all last?

Just a couple of minutes. The longest time will be in Illinois, where it will last 2 minutes and 40 seconds, though it won't be all that much shorter everywhere else.

The true joy of an eclipse is in the build-up and the changes, though, so you can certainly drag it out. Make sure to spend a little time outside before the eclipse arrives, so that you get accustomed to the light; that will make the eerie darkness when the moon blocks out the sun even more strange.

Where will it happen?

Everyone in North America will be able to see some of the eclipse. But not everyone will see all of it.

The "path of totality will arrive in the north west, arriving first at Lincoln City in Oregon at 9.05am pacific daylight time. It will then spread across the US, going east more quickly than it goes south, and will leave the US at Charleston, South Carolina, at 2.43pm local time.

(Nasa (Nasa)

If you'd like more specific information about where and when the eclipse will be passing over where you live, then it's probably best to consult Nasa's special page which is full of very detailed eclipse maps showing the route and times. But it's also worth remembering that you'll see some of it wherever you are, and that the eclipse will be moving quickly – so long as you're outside at roughly the right time, you'll see something spectacular.

What if you're not in the path of totality, or somewhere else entirely like Europe?

Eclipses aren't either off or on – the path of totality shows where the moon will cover the sun entirely, but outside of that there'll be lots to see too.

Nasa jets will chase the total solar eclipse across the US