Which planet has the longest day?

The planet with the longest day is Venus. A day on Venus, which is defined as the time it takes for Venus to complete one rotation on its axis, lasts about 243 Earth days. This is notably longer than its year, as Venus takes only about 225 Earth days to complete one orbit around the Sun.

One of the intriguing aspects of Venus is its retrograde rotation; it spins in the opposite direction to most planets in the solar system. This unusual rotation, combined with its elongated period of rotation, results in a day that is longer than the time it takes to orbit the Sun.

In contrast, the other planets listed have much shorter rotational periods. For instance, Earth has a day of 24 hours, Mars has a day of approximately 24.6 hours, and Jupiter, which is the largest planet, has an incredibly short rotational period of about 9.9 hours. This stark difference highlights why Venus is distinctive in its rotation relative to all the planets in the solar system.