How long is a day on Venus?

A day on Venus is really long. But we have to clarify two definitions of day before we can proceed further. There are sidereal day and solar day. On Earth, a sidereal day lasts 23 hours 56 minutes and 4.1 seconds, a solar day lasts exactly 24 hours, as expected. A solar day means a day from the sun’s perspective. A sidereal day is a day from the perspective of a distant star. Equivalently, a sidereal day is when a planet rotates one full cycle along its axis.

For Earth, there is not much difference between sidereal day and solar day. For Venus, a sidereal day is 243 Earth days and a solar day is 116.75 Earth days. There is a huge difference.

By the way, a year on Venus is 225 Earth days. It takes longer for Venus to rotate one cycle along its own axis than to rotate one cycle along the sun. A (sidereal) day is longer than a year on Venus.

Among all planets, Venus has the longest day. Among all planets, Venus rotates against the direction of its revolution around the sun. On Venus, the sun rises at the west and sets on the east. It is the only planet where a sidereal day is longer than a solar day.

Reference

https://www.universetoday.com/14282/how-long-is-a-day-on-venus/