The reason that it does not work is that Creation Date and Today() do not have the same data types. Creation Date is a datetime, but Today() is a date.
When comparing them, the value of Today() will be typecast to datetime, using midnight as the time (so dd/mm/yyyy will become dd/mm/yyyy 00:00)
In general, you can use DateTime >= Today() and DateTime < (Today() + Days(1))
but actually in your specific case, [Creation Date] >= Today() will suffice, since there can’t be any items with a creation date after midnight tomorrow(!)