The following code is working perfectly in my system to update a date characteristic
DATA: okey TYPE bapi1003_key-object,
otable TYPE bapi1003_key-objecttable VALUE 'MCH1',
classnum TYPE bapi1003_key-classnum VALUE 'PF',
classtype TYPE bapi1003_key-classtype VALUE '023'.
DATA: numnews TYPE TABLE OF bapi1003_alloc_values_num,
numnew TYPE bapi1003_alloc_values_num,
charnews TYPE TABLE OF bapi1003_alloc_values_char,
currnews TYPE TABLE OF bapi1003_alloc_values_curr,
bret TYPE TABLE OF bapiret2,
ret TYPE bapiret2.
DATA: atwrt TYPE atwrt.
CHECK ck_test IS INITIAL.
numnew-charact = 'ZDATAUM'.
atwrt = out-budat.
CALL FUNCTION 'CTCV_CONVERT_DATE_TO_FLOAT'
EXPORTING
date = atwrt
IMPORTING
float = numnew-value_from.
APPEND numnew TO numnews.
okey(18) = out-matnr.
okey+18(10) = out-charg.
CALL FUNCTION 'BAPI_OBJCL_CHANGE'
EXPORTING
objectkey = okey
objecttable = otable
classnum = classnum
classtype = classtype
TABLES
allocvaluesnumnew = numnews
allocvaluescharnew = charnews
allocvaluescurrnew = currnews
return = bret.
LOOP AT bret INTO ret WHERE type = 'E' OR type = 'A'.
out-message = ret-message.
EXIT.
ENDLOOP.
IF sy-subrc = 0.
out-status = icon_failure.
CALL FUNCTION 'BAPI_TRANSACTION_ROLLBACK'.
ELSE.
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'.
out-status = icon_checked.
out-message = 'Batch classification updated'(001).
ENDIF.
