Check user settings/SU01. It should work even with simple FM conversion.
DATA: l_date TYPE dats.
PARAMETERS: p_date TYPE char8.
WRITE p_date TO l_date USING NO EDIT MASK.
CALL FUNCTION 'CONVERSION_EXIT_ALPHA_OUTPUT'
EXPORTING
input = p_date
IMPORTING
output = l_date.
WRITE l_date.