How Long Is a Day on Venus? (And Why It's Longer Than a Year)

A single day on Venus lasts longer than a whole year on Venus.

Yes, you read that correctly. On Venus, you'd actually have your next birthday before you'd finished today.

How is that even possible? It comes down to two weird things Venus does. It spins really, really slowly. And it spins backwards. Let's unpack both, starting with the slowness.

How Long Is One Day on Venus?

A day on Venus lasts about 243 Earth days.

That's how long it takes Venus to spin all the way around once. Earth zips around once every 24 hours. Venus is the slowest spinner in the entire solar system. It takes 5,832 hours just to manage a single rotation.

If you actually lived on Venus, you'd spend a lot of time waiting for things. The Sun would inch across the sky so slowly you'd practically forget it was moving. Sunrise to sunset would take about 117 Earth days. So if you started a sandwich at sunrise on Venus and waited until sunset to eat it, your sandwich would be older than your little brother.

Why is Venus so slow? Mostly because of its enormous, heavy atmosphere. The air is so thick (92 times heavier than Earth's air) that it actually drags on the planet's spin, slowing it down over billions of years.

How Long Is One Year on Venus?

A year on Venus is 225 Earth days.

That's how long it takes Venus to make one full lap of the Sun. Earth needs 365 days to do its lap. Venus is closer to the Sun, so it has a shorter racetrack to run, and it gets round its orbit faster than we do.

A Day Longer Than a Year? Hold On.

Yes. Venus is the only planet in the solar system where a single day is longer than a year. Here's the comparison side by side:

• One day on Venus: 243 Earth days (one full spin)
• One year on Venus: 225 Earth days (one full lap of the Sun)

So Venus laps the Sun before it can finish spinning around. Imagine running so slowly around a track that the lap is over before you've taken one full step. That's basically Venus.

Practically, this means a "year" on Venus is shorter than a "day" on Venus by about 18 Earth days.

Sidereal Day vs Solar Day Made Easy

Here's a slightly trickier bit, but stick with me, because it's quite interesting.

When scientists say "a day," they actually mean two slightly different things:

• A sidereal day is how long it takes a planet to spin once on its axis, measured against the stars. For Venus, that's the famous 243 Earth days.
• A solar day is the time from one sunrise to the next. On Earth that's almost the same as the sidereal day. But on Venus, because of the planet's weird backwards spin, the solar day is only about 117 Earth days long.

So if you measured a Venusian day as "the time between two sunrises," it's actually shorter than a Venus year. Either way, you've got an absurdly long day on your hands.

Why Does Venus Spin Backwards?

Almost every planet in our solar system spins in the same direction. If you looked down at the solar system from above the North Pole, you'd see the planets all spinning anticlockwise.

Venus does the opposite. It spins clockwise.

Scientists call this retrograde rotation, which is just a posh way of saying "the wrong way round." It's strange, and we don't fully know why it happens. There are two main theories.

The most popular idea is that, billions of years ago, a huge object — possibly another protoplanet or a giant asteroid — slammed into Venus and flipped it almost upside down. Once flipped, Venus would appear to spin "backwards" from the rest of the solar system, even though nothing about its actual rotation changed.

The other idea is that Venus's atmosphere has been doing the work. Its air is so thick and heavy that it might have been slowly braking the planet's spin over billions of years, eventually stopping it and pushing it gently in the opposite direction. We do know that Venus's day length actually changes by about 20 minutes from year to year, which suggests the atmosphere is still messing with the planet's spin today.

What Does This Mean for Sunrise and Sunset?

If you somehow stood on Venus's surface (in some kind of impossible spacesuit), and you could see through the thick clouds, the Sun would rise in the west and set in the east. Exactly opposite to Earth.

You also wouldn't see the sunset arrive any time soon. Because Venus spins so slowly, the Sun would crawl across the sky over the course of about 117 Earth days. You could go to school for two whole months between mid-morning and lunchtime. That's how slow we're talking.

And the Sun itself would look weird. Venus's atmosphere is so thick that sunlight gets bent, scattered, and filtered by the time it reaches the ground. The whole sky would look orange. Sunlight would feel softer and dimmer than at home, even though the Sun is closer.

Bedtimes would be a nightmare to negotiate.

Frequently Asked Questions

Keep Exploring Venus

• Venus Facts for Kids — The Complete Guide
• Why Is Venus Called the Morning Star?
• Venus vs Earth — How Are They Different?