I talked with a colleague about that over lunch today. It is possible that
someone might set a time the same as another just to see what happens or
to mess up the works. A possible solution would be to accept no data
that is more than a day old and display only data that is more than a
day old. Then those inputting would not have access to data put in
by others covering the same time period. Of course, windows for entering
and displaying could be longer than a day, but spurious duplication
is a real concern here.