function cDate (expr as variant) as date function cvDate(expr as variant) as variant
cDate returns a date and cvDate returns a variant. Thus, the expression cvDate(null) is valid while cDate(null) raises run-time error 94: Invalid use of Null. dt is a numeric type, it is interpreted (cast) as double which represents (fractional) days since midnight 1899-12-30 (See here). dt it is a string, it is tried to be interpreted according to the locale currently in effect (which is not always possible).