A much used figure of speech, but as it turns out there aren’t really 24 hours in a day.
There are actually only 23 hours, 56 minutes and 4.1 seconds in a day. This is the time it takes for the earth to rotate on its axis, and is known as a sidereal day.
But saying I’m available 23h 56″ 4.1’/7 just will not cut it, will it?