MATLAB: How to change a variable to a time variable

datedatetimeimporting excel datatimetimestamp

I have the following excel file (ejemplo.xlsx) where the first column is date (format yyyy-MM-dd) , the second start hour and the third is last hour. How can I tell Matlab that the second and third columns are datetime variables? I tried the following code but is not working. 
Ej = readtable('Ejemplo.xlsx'); 
ej  = table2timetable(Ej); 
ej= datetime(ej.StartTime,'Format','HH:mm')
Thanks in advance!

Best Answer

One approach: 
Ej = readtable('Ejemplo.xlsx');
Ej.StartTime = Ej{:,1} + days(Ej{:,2});
Ej.EndTime = Ej{:,1} + days(Ej{:,3});
with: 
FirstFiveRows = Ej(1:5,:)
producing: 
FirstFiveRows =
  5×5 table
       Date             StartTime                EndTime           ForecastInMW    ActualInMW
    ___________    ____________________    ____________________    ____________    __________
    01-Sep-2010    01-Sep-2010 00:00:00    01-Sep-2010 00:15:00       1037.6          983.3  
    01-Sep-2010    01-Sep-2010 00:15:00    01-Sep-2010 00:30:00       1071.2         1177.7  
    01-Sep-2010    01-Sep-2010 00:30:00    01-Sep-2010 00:45:00       1098.5         1397.7  
    01-Sep-2010    01-Sep-2010 00:45:00    01-Sep-2010 01:00:00       1339.1         1414.4  
    01-Sep-2010    01-Sep-2010 01:00:00    01-Sep-2010 01:15:00       1360.4         1585.1
EDIT — (8 Sep 2020 at 16:02)
To use my code with 'PreserveVariableNames',true (and avoiding the Warning that appears otherwise), my code changes slightly to: 
Ej = readtable('Ejemplo.xlsx', 'PreserveVariableNames',1);
Ej.('Start Time') = Ej{:,1} + days(Ej{:,2});
Ej.('End Time') = Ej{:,1} + days(Ej{:,3});
with: 
    FirstFiveRows = Ej(1:5,:)
producing: 
FirstFiveRows =
  5×5 table
       Date             Start Time               End Time          Forecast in MW    Actual in MW
    ___________    ____________________    ____________________    ______________    ____________
    01-Sep-2010    01-Sep-2010 00:00:00    01-Sep-2010 00:15:00        1037.6            983.3   
    01-Sep-2010    01-Sep-2010 00:15:00    01-Sep-2010 00:30:00        1071.2           1177.7   
    01-Sep-2010    01-Sep-2010 00:30:00    01-Sep-2010 00:45:00        1098.5           1397.7   
    01-Sep-2010    01-Sep-2010 00:45:00    01-Sep-2010 01:00:00        1339.1           1414.4   
    01-Sep-2010    01-Sep-2010 01:00:00    01-Sep-2010 01:15:00        1360.4           1585.1
.
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