Orbit and Rotation of Neptune. Because Neptune is not a solid body, its atmosphere undergoes differential rotation. Despite this fact, it never appears in the same position in our sky because the Earth would have rotated in a different location during its 365.25 day orbit. The average distance between the Sun and Neptune is 4.55 billion km, and Neptune completes its orbit every 164.79 years; a year on Neptune is 164.79 Earth years. Neptune's rotation period about axis is 17.24 hours, while Neptune's revolution period about the Sun is 165 years. Rotation period (length of day in Earth days) 0.67 (19.1 hours) Revolution period (length of year in Earth days) 60,190 (164.8 Earth years) Obliquity (tilt of axis degrees) 29.6 Orbit inclination (degrees) 1.77 Orbit eccentricity (deviation from circular) 0.009 Mean temperature (K) 48