A day on Mercury is equivalent to 58 Earth days.

 

A day on Mercury is equivalent to 58 Earth days.

A planet's day is the time it takes the planet to rotate or spin once on its axis. Mercury rotates very slowly compared to Earth so a day on Mercury is much longer than a day on Earth. A day on Mercury is 58.646 Earth days or 1407.5 hours long while a day on Earth is 23.934 hours long.

Mercury orbits the Sun every 87.97 days which is the shortest orbit of all the planets in the solar system. Mercury is tidally locked with the Sun and the only planet to do so, like our moon facing Earth. It has a 3:2 spin-orbit resonance meaning it rotates on its axis three times for every two times it orbits the Sun meaning a day is extremely long, in fact it has the longest day of the planets in the solar system. Mercury’s day has a sidereal day and a solar day like here on Earth. As Earth rotates once on its axis it is a sidereal day, however as you stand on the exact same spot from where the Sun was the previous day it is a solar day and is 4 minutes longer. A sidereal day on Mercury lasts 58 days 15 hours and 30 minutes which is how long the planet takes to rotate once on its axis. A solar day on Mercury lasts 176 days meaning if you were standing on exact same spot from where the Sun was in the next 176 days it would be a solar day on Mercury.