I personally wondered myself if when they say a 24 hour carb up if they mean 24 hours of waking -eating time or what, but then I realized that 24 hrs. means however many hours you are awake for a given day. I mean if it went by only how many hours you were awake, your carb up[ would go on for like 4 days in most general carb up specifications.
anyway, why are you carbing up? Are you dieting? Are you glycogen depleted? Do you know the right ways to carb up? Please click the links at the top of the forum and go read mr.x's ckd manual for the info.