How to sort the dataframe to get correct result?

[MetalComm]

Hi all! I would like to ask you a question.

I noticed that applying the formula
ParamsEstimation.covar_matrix(X, method='ewma1')
the result changes if the dataframe X is sorted ascending or descending by the datetime column.

I would like to know which way the dataframe should be sorted to return the correct result.

Thank you very much.