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How long is a day on Jupiter?

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photo of Jupiter taken by Voyager 1 — Jupiter Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7 million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud bands and Great Red Spot (lower centre).

Because Jupiter is a gas giant without a solid surface, it does not have a single, uniform rotation period. Instead, its rotation varies by latitude and internal structure, leading to three defined systems:1

System I: 9 hours, 50 minutes, 30 seconds (equatorial regions)1
System II: 9 hours, 55 minutes, 41 seconds (higher latitudes)1
System III: 9 hours, 55, minutes, 29 seconds (the planet's magnetic field and interior)1

System III is considered the true rotation period of the planet because it reflects the rotation of Jupiter's massive interior, where the magnetic field is generated. Generally, it is accurate to say that Jupiter rotates once about every 10 hours.12