Call readtable. Reassemble the date and time string into one block of text then call datetime to convert that text representation into a datetime array.
t = readtable('answer428720.csv')
t.str = t.Var1 + " " + string(t.Var2)
fmt = 'yyyyMMdd HH:mm:ss.SSSSSSSSS';
t.timestamp = datetime(t.str, 'InputFormat', fmt, 'Format', fmt)
You could modify the readtable call or the import options to do this in fewer lines of code, but this is fairly readable IMO.
