A timetable can contain many different types of data, some of which define element-wise multiplication and some of which don't. The easiest way to perform arithmetic on a specific numeric variable in a timetable is to index into the timetable.
thedates = datetime('today')+days(0:5);
TT = array2timetable(magic(6), 'RowTimes', thedates)
y = TT.Var3 .* TT.Var5
If you want to perform the same operation on all numeric variables in your timetable you can do that using vartype.
y2 = TT{:, vartype('double')}.^2
TT{:, vartype('double')} = y2
If the data stored in the timetable can be concatenated into a numeric array, you could reference all of it at once.
TT.Variables = sqrt(TT.Variables)
