Is there a completely reliable method of adding months to a date in ABAP?

Question

Does anyone know of a completely reliable and consistent ABAP function module that can be used to add months to a date.  One that will always get the correct last day of the month when requested to add 1 month to the last day of the previous month.  Something as reliable as using the ADD_MONTHS function in Oracle SQL.  I don't want to use any of the specific 'get last day of the month' function modules since the start date may not necessarily be the last day of a month.
In the past I have trusted the following.  Now they have betrayed me. 
MONTHS_PLUS_DETERMINE  
Correctly provides 28.02.09 when adding 1 months to 31.01.09.
Incorrectly gives me 28.03.09 instead of 31.03.09 when adding 1 month to 28.02.09
RP_CALC_DATE_IN_INTERVAL and RP_CALC_DATE_IN_INTERVAL_SG
Both incorrectly give me 01.03.09 when asked to add 1 month to 31.01.09.
Both incorrectly give me 28.03.09 when asked to add 1 month to 28.02.09.
We're on ECC6.

Answer 1

>
Suhas Saha wrote:
> Hello Christine,
>
> Did you check the method ADD_MONTHS_TO_DATE of the class CL_HRPAD_DATE_COMPUTATIONS ?
>
>
> *     Adds No. of Months to Date
>       TRY.
>           CALL METHOD cl_hrpad_date_computations=>add_months_to_date
>             EXPORTING
>               start_date = sy-datum
>               months     = l_v_month
>             RECEIVING
>               date       = l_v_date.
>         CATCH cx_hrpa_violated_postcondition .
>       ENDTRY.
>
>
> I dont have any idea how ADD_MONTHS function in Oracle SQL works, though ):
>
> Hope this helps.
>
> BR,
> Suhas
That also sometimes works.....but adding 1 month to 28.02.2009 gives me 28.03.2009 and adding 1 month to 29.02.2008 gives me 29.03.2008.
This is how to use ADD_MONTHS in Oracle SQL - a bit naughty since you have to use native SQL to do it but it ALWAYS seems to work.  I pass a date, month number and + or - into the function module.
* For use with class based exception CX_SY_OPEN_SQL_DB.
DATA:
  ex_check_os       TYPE REF TO cx_sy_open_sql_db,
  ex_check_rs       TYPE REF TO cx_sy_native_sql_error,
  ex_result(200)    TYPE C,
  ex_text           TYPE STRING,
  lv_new_date       TYPE datum,
  lv_old_date       TYPE datum,
  lv_months         TYPE I.
  lv_old_date = iv_date.
  lv_months = iv_months.
  IF iv_sign = '-'.
     lv_months = lv_months * -1.
  ENDIF.
  TRY.
    EXEC SQL.
      SELECT to_char(add_months(to_date(:lv_old_date,'YYYYMMDD'),:lv_months),'YYYYMMDD')
      INTO :lv_new_date
      FROM sys.dual a
    ENDEXEC.
    CATCH cx_sy_native_sql_error INTO ex_check_rs.
    ex_text = ex_check_rs->get_text( ).
    ev_error_message = ex_text.
    ev_return = 4.
  ENDTRY.
  ev_return = 0.
  ev_date = lv_new_date.