METHOD check_date .
* Einzeldatums-Check
  IF NOT flug_input-vondatum IS INITIAL.
    CALL FUNCTION 'DATE_CHECK_PLAUSIBILITY'
      EXPORTING
        date                      = flug_input-vondatum
      EXCEPTIONS
        plausibility_check_failed = 1
        OTHERS                    = 2.
    IF sy-subrc <> 0.
      cursor = 'vondatum'.
      MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
              WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4
              INTO mess.
      page->messages->add_message(
        condition = cursor
        message = mess ).
    ENDIF.
  ENDIF.
* Einzeldatums-Check
  IF NOT flug_input-vondatum IS INITIAL.
    CALL FUNCTION 'DATE_CHECK_PLAUSIBILITY'
      EXPORTING
        date                      = flug_input-bisdatum
      EXCEPTIONS
        plausibility_check_failed = 1
        OTHERS                    = 2.
    IF sy-subrc <> 0.
      cursor = 'bisdatum'.
      MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
              WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4
              INTO mess.
      page->messages->add_message(
        condition = cursor
        message = mess ).
    ENDIF.
  ENDIF.
* check "von <= bis"
  IF flug_input-vondatum > flug_input-bisdatum.
    cursor = 'datumsbereich'.
    MESSAGE e001 WITH flug_input-vondatum flug_input-bisdatum
      INTO mess.
*   Vondatum & liegt vor Bisdatum &.
    page->messages->add_message(
      condition = cursor
      message = mess ).
  ENDIF.
ENDMETHOD.