what is the length of mercury's day
One day on Mercury is equal to 1407.6 Earth hours. The length of day on Mercury is 58.646 Earth days. That's the rotation time, which is the sidereal day, but there's also the solar day. 58.6 Earth days. Mercury is the closest planet to the Sun and takes 88 days to  complete one orbit. This means that a year on Mercury lasts 88  days.