When a data table is moved to a Report format by using << Get As Report, it is moved into a Table Box object, not into a Text Box. And even more specifically, since Date is a numeric column, it is moved into a Number Col Box object which is right justified. Looking into the Script Index, for Number Col Box I do not see any way to change the justification, for a Number Col Box.
A solution to your problem would be to change the Data Type of the Date column to Character in the data table. Then do your Get As Report,. Then your Date column will be moved into a String Col Box object, which is left justified.
Jim