DateTimeException if the two intervals do
not intersect or if the given interval is empty.
Example: -------------------- assert(PosInfInterval!Date(Date(1996, 1, 2)).intersection( Interval!Date(Date(1990, 7, 6), Date(2000, 8, 2))) == Interval!Date(Date(1996, 1 , 2), Date(2000, 8, 2)));
assert(PosInfInterval!Date(Date(1996, 1, 2)).intersection( Interval!Date(Date(1999, 1, 12), Date(2011, 9, 17))) == Interval!Date(Date(1999, 1 , 12), Date(2011, 9, 17))); --------------------