A day on Venus is longer than its year

On Venus, you could celebrate your birthday before the Sun finished setting. The planet takes about 243 Earth days to turn once on its axis, but only about 225 Earth days to complete a full orbit of the Sun. In other words, one Venusian day lasts longer than one Venusian year — the only major planet where that’s true.

Venus rotates absurdly slowly, the most sluggish spin in the solar system. Its dense, superheated atmosphere is thought to act like a brake, dragging on the surface and helping keep the rotation locked into this crawl.

Spin and orbit are nearly matched, so Venus barely turns as it loops the Sun.

Stranger still, Venus spins backwards. Almost every planet rotates the same direction it orbits, but Venus turns the opposite way — likely the legacy of a colossal ancient impact, or its thick atmosphere flipping it over time. From the surface, the Sun would rise in the west and set in the east.

Because the slow backward spin combines with the orbital motion, the interval from one sunrise to the next — the true solar day — works out to about 117 Earth days. So the Sun comes up roughly twice during a single Venusian year, even though the planet has technically turned less than once on its axis.