Calculated date

Hello

I have a strange behaviour in directquery . I have a table with a column containing the number of days since 1957/01/01. I would like to reconstruct the corresponding date.

I have used the calculated column using the following function : date(1957,01,[DATE1]+1). I have no error but I am not able to display the column in a grid nor use it in any visual.

Any help will be much appreciated