Next calendar date according to which calendar? Not all places in the world are on the same date, so if you don't indicate the timezone, there's no way to tell what the next calendar date is.

I suppose due to DST, the same clock time on the next calendar date might not exist or be ambiguous.

Conversely, +24 hours may fall on the same calendar date or two calendar days on from now.

Really, "tomorrow" should be the interval from the beginning of the next calendar date to the end.