What Are the Durations of Days and Years on Other Planets in Our Solar System?

The length of a day is such a fundamental part of life on Earth that it's almost impossible to imagine what time would even mean without it. How would we define a satisfying night’s sleep if a day were just 10 hours long instead of 24? Or if a single day spanned thousands of hours—how would our daily routines adapt to such extreme cycles of light and darkness? The same thought process applies to a year. How would we view “seasons” if Earth only took 88 days to orbit the sun? What would our calendar even look like?

These are the kinds of intriguing questions you’ll find yourself asking as you explore the varying day and year lengths of the other planets in our solar system. To clarify: A day refers to the time it takes for a planet to complete one full rotation on its axis, while a year refers to the time it takes for the planet to orbit the sun.

You may be shocked to discover just how drastically the other planets’ day-to-year ratios differ from Earth’s. For instance, not every planet spins on its axis faster than it orbits the sun. On Venus, a day is actually longer than a year: It takes Venus 243 Earth days to complete one full rotation, while it only takes 225 Earth days to finish one full orbit around the sun. In contrast, a day on Neptune is about 8 hours shorter than an Earth day, but the planet only completes a full orbit once every 165 Earth years.

Take a look at the remaining stats below. (The decimals have been rounded, and Earth’s days and years can slightly vary over time, so treat these numbers as approximations.)

1. Mercury

• Day length = 58.67 Earth days (1408 hours)
• Year length = 88 Earth days (0.2 Earth years)

2. Venus

• Day length = 243 Earth days (5832 hours)
• Year length = Approximately 225 Earth days (0.6 Earth years)

3. Mars

• Day length = 1.04 Earth days (roughly 25 hours)
• Year length = 687 Earth days (1.9 Earth years)

4. Jupiter

• Day length = 0.42 Earth days (10 hours)
• Year length = 4333 Earth days (11.9 Earth years)

5. Saturn

• Day length = 0.46 Earth days (approximately 11 hours)
• Year length = 10,756 Earth days (29.4 Earth years)

6. Uranus

• Day length = 0.71 Earth days (approximately 17 hours)
• Year length = 30,687 Earth days (around 84 Earth years)

7. Neptune

• Day length = 0.67 Earth days (16 hours)
• Year length = 60,190 Earth days (165 Earth years)

Special Mention: Pluto

• Day length = approximately 6 Earth days (153 hours)
• Year length = 90,520 Earth days (248 Earth years)