I am suggesting that Wednesday would continue to run from midnight to midnight, but in a world where "midnight" means "midnight UTC" rather than "midnight in an appropriate local time zone", the block of time occupied by Wednesday would be less useful. I am concluding that having the entire world use UTC as its local time is not practical.
See also California, when the day of the week would change while you were at work in the afternoon.
(Did you mean for your comment to be in reply to sxp or zanny, not me?)