That depends on what you consider "one day." Is it when the rotates around relative to the sun or to the stars? A solar day is 4 minutes longer than a sidereal day. A sidereal day is 23 hours, 56 minutes, and 4.091 seconds.
The day that I consider a "day" is the day that is used to calculate our calendars. The one that requires a leap day every 4 years to keep things on the beam.
Now if you want to have a really interesting discussion...how long was a "day" back in the Book of Genesis?
I have to go to bed. So feel free to discuss among yourselves.