What is the length of the day on Venus?

A day of Venus from the surface of Venus lasts 2,802 Earth hours, which corresponds to 116.75 Earth days. The year of Venus, i.e. the time it takes Venus to move one revolution around the Sun, is 225 Earth days approximately twice as long.

In some places, you can read that the day of Venus is longer than the year of Venus, but it is based on a misunderstanding of what the day is.

On Earth, we are talking about the so-called stellar day, and the solar day. A star’s day is the time it takes the Earth to rotate once on its axis.

A solar day is the time it takes from the time an observer on the planet’s surface sees the sun at the top of the sky until it’s at the top of the sky again the next day. Thus, a solar day is what we usually mean by the term day.

On Earth, the average sidereal day is 23 hours 56 minutes and 4.1 seconds, while the average solar day is exactly 24 hours. On Venus, a sidereal day lasts 243.03 Earth days, longer than a Venus year, while a solar day is said to be 116.75 Earth days.

The difference between the solar day and the star’s day arises because the planet, as it rotates, also moves in its one-year orbit around the sun. It is the movement around the sun along with the planet’s rotation on its axis that determines the length of the solar day.

Because the Earth rotates on its axis in the same direction that it revolves around the Sun, a star’s day on Earth is shorter than the Sun’s. However, Venus rotates in the opposite direction on its axis relative to its rotation around the Sun. This makes Venus’ days longer than her solar days.