Convert date to posting date

Posting date = date comptable.
Use the FM below :

  CALL FUNCTION 'FIRST_DAY_IN_PERIOD_GET'
    EXPORTING
      i_gjahr        = gv_gjhar
      i_periv        = gc_24
      i_poper        = gv_poper
    IMPORTING
      e_date         = s_fkdat-low
    EXCEPTIONS
      input_false    = 1
      t009_notfound  = 2
      t009b_notfound = 3
      OTHERS         = 4.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
    WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.

  CALL FUNCTION 'LAST_DAY_IN_PERIOD_GET'
    EXPORTING
      i_gjahr        = gv_gjhar
      i_periv        = gc_24
      i_poper        = gv_poper
    IMPORTING
      e_date         = s_fkdat-high
    EXCEPTIONS
      input_false    = 1
      t009_notfound  = 2
      t009b_notfound = 3
      OTHERS         = 4.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
    WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.

Search tag: date comptable, conversion