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One Earth day is equal to 23 hours, 56 minutes and 4.1 seconds (the time required to complete a single rotation of the Earth).
How long is a day on Mercury? 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. Cool Cosmos is an IPAC website. Based on Government Sponsored Research NAS7-03001 and NNN12AA01C.