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The Venus length of day is 243 days.
But the story is a little stranger than that. Venus is actually rotating backwards compared to the rest of the planets in the Solar System. Seen from above the north pole, Venus is slowly rotating in a clockwise direction. Compare this to Earth and the rest of the planets, which rotate in a counter-clockwise direction.
And it gets even stranger, when you consider that a year on Venus only lasts 224.7 days. In other words, a day on Venus is actually longer than a year on Venus. If you could actually stand on the surface and see the Sun, you would see the Sun rise in the West, and pass through the sky over the course of 116.75 days and then set in the East. So a solar day on Venus is 116.75 days.
Astronomers aren’t sure why the length of day on Venus takes so long, and why Venus is rotating backwards. It’s possible that Venus was struck by a large object early on in its history, which flipped it over and caused its strange rotation.
We’ve written many articles about the day length of the planets, here’s an article about a day on Mars, and here’s an article about a day on Saturn.
If you’d like more info on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.
We’ve also recorded an episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.