No, and it wouldn't correctly handle the cases where you have a year only.
If you can read it in from a text file you can control the format, but not Excel.
You can use INPUT to convert the dates that are full dates but you'll need to handle the years only or missing separately.
if length(date) = 10 then new_date = input(date, mmddyy10.);
else if length(date)=4 then new_date = mdy(7, 1, input(date, 4.));
else if missing(date) then new_date = .;