While a uniform time would eliminate one problem, it would create another. If it were midnight at the same time worldwide, for some it would mean breakfast time while for others it would mean sleeping time. Our whole concept of time of day would be completely out of whack with respect to others.
Until all of a sudden people notice "Hey, I need to wake up at 12:00 (07:00 + 05:00) to be at work at 13:00 (08:00 +05:00), and I get off work at 21:00 (16:00 +05:00).
It's not rocket science. If your Boss tells you that you have to be present at a certain hour, then you figure out what your sleep pattern is, and you figure out how to be there on time. Like I said, not rocket science.
With Indiana's recent decision to move to daylight savings time, I'm considering moving to Arizona or Hawaii (the two last states with any sense)
 I use +5 because Indiana used to be just plain -5, and because it makes rather simple math.