Additionally, either the calendar day boundary is tied to 00:00 new-UTC, which would be incredibly awkward for everybody not living near wherever the meridian ends up (which invariable will be a large fraction of the world's population, no matter which meridian you end up choosing), because now all of a sudden the calendar day changes in the middle of everybody's waking hours (public holidays starting and stopping at e.g. 2 o'clock in the afternoon anyone?), or else each location needs to offset the calendar date change by some suitable value so it ends up roughly were it used to be (i.e. at a time when most people sleep), which again means basically re-introducing time zones through the back door.