You cannot concatenate together data of types datetime and double without converting the datetime array to double or the double array to datetime. But that's probably not what you want.
If you were using release R2016b or later I would suggest creating a timetable array from your data, but you indicated you're using R2016a. If you cannot upgrade to release R2016b or later I think you're probably going to want to create a table array instead. [The table data type was introduced in release R2013b.] Let's make some sample data.
v = (0:4).';
dt = datetime('today') + days(v);
x = v.^2;
Now let's build the table.
T = table(dt, x)
See the documentation for table to learn how to work with data stored in a table.
doc table
One example: you can extract the row of the table corresponding to x = 4.
T(T.x == 4, :)
