your date entry is in A1
try this formula
=IF(AND(A1>="1/1/94"+0,A1<="12/31/95"+0),"U16",IF(AND(A1>="1/1/96"+0,A1<="12/31/97"+0),"U14",IF(A1>=1/1/98,"U12","")))
study this carefully so that you an create such a formula in future
remember in excel the dates are entered as mm/dd/yy
that is 5/10/94 is 10th May 1994