In R2016b, the variable names must be valid MATLAB variable names. (That changed in R2020a, so what you want to do would be permitted.)
The other problem you are having is that the dates in column #1 need to be a datetime array.
This does everything except use the variable names you want:
M = [19790101 7839.4 29.4 17.3 1.6 51.8 13.8 5.2
19790102 8046.4 30.1 17.5 0.1 45.2 16.2 4.9
19790103 9018.2 27.6 13.5 0 40.9 14.3 5.2
19790104 5359.4 21.8 14.4 0.2 61.5 8 4.9
19790105 8145.9 26.4 13.6 0.7 52.2 11.2 3.8 ];
T1 = array2table(M);
DT = datetime(num2str(M(:,1)), 'InputFormat','yyyyMMdd');
T1.M1 = DT
producing:
T1 =
5×8 table
M1 M2 M3 M4 M5 M6 M7 M8
___________ ______ ____ ____ ___ ____ ____ ___
01-Jan-1979 7839.4 29.4 17.3 1.6 51.8 13.8 5.2
02-Jan-1979 8046.4 30.1 17.5 0.1 45.2 16.2 4.9
03-Jan-1979 9018.2 27.6 13.5 0 40.9 14.3 5.2
04-Jan-1979 5359.4 21.8 14.4 0.2 61.5 8 4.9
05-Jan-1979 8145.9 26.4 13.6 0.7 52.2 11.2 3.8
Change the variable names to versions of what you have that will work in R2016a. Even if you change them to what you want in the file, they will be changed to valid MATLAB variable names when you import it. Your only option is to upgrade to R2020a or later to use the variable names you want to use.
You can then use writetable with ‘T1’ (or whatever you wish to name it in your code).
EDIT — (16 Nov 2020 at 20:40)
To have the datetime column in the original format, add the 'Format' name-value pair to the datetime call in the ‘DT’ assignment:
DT = datetime(num2str(M(:,1)), 'InputFormat','yyyyMMdd', 'Format','yyyyMMdd');
The rest of the code is unchanged.
M1 M2 M3 M4 M5 M6 M7 M8
________ ______ ____ ____ ___ ____ ____ ___
19790101 7839.4 29.4 17.3 1.6 51.8 13.8 5.2
19790102 8046.4 30.1 17.5 0.1 45.2 16.2 4.9
19790103 9018.2 27.6 13.5 0 40.9 14.3 5.2
19790104 5359.4 21.8 14.4 0.2 61.5 8 4.9
19790105 8145.9 26.4 13.6 0.7 52.2 11.2 3.8
.
