Try this:
D = xlsread('dates.xlsx');
Ds = num2str(D,'%d');
Dn = datenum(Ds, 'yyyymmdd');
Check = datevec(Dn) % Check Conversion (Delete Later)
The first five :
Check =
1986 1 2 0 0 0
1986 1 3 0 0 0
1986 1 6 0 0 0
1986 1 7 0 0 0
1986 1 8 0 0 0
