With a number in A1:
=IF(LEN(A1)=7,DATE(RIGHT(A1,4),LEFT(A1,1),MID(A1, 2,2)),DATE(RIGHT(A1,4),LEFT(A1,2),MID(A1,3,2)))

This is a more compact way to do the same thing...

=--TEXT(A1,"00\/00\/0000")

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Rick (MVP - Excel)