Well, that depends. (Don't you hate that answer?)
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| NASA photo |
The sun is complicated, more so than the planets. It's big, gaseous, and of course, a simple understanding of a day, ours anyway, is the time it takes for the sun to pass overhead. That definition won't work here.
The easiest answer is that of a sidereal day, a day in which the stars are the time keepers. A star can be found at one location in the sky one night and then the time it takes to find the star in that same position the next night is a sidereal day. For Earth, that is about 23 hours and 56 minutes, or 24 hours if you round up.
But even this solution to the question depends on where one is standing on the Sun as different parts of the Sun rotate at different speeds. At the equator, it would take approximately 24.5 Earth days while at the poles about 34 Earth days.
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