Bug with interval and leap years

Question

select to_date('2012-feb-29','yyyy-mon-dd') + interval '1' year as dt from dual;
ORA-01839: date not valid for month specified
01839. 00000 -  "date not valid for month specified"
*Cause:   
*Action:
select to_date('2012-feb-29','yyyy-mon-dd') + interval '2' year as dt from dual;
ORA-01839: date not valid for month specified
01839. 00000 -  "date not valid for month specified"
*Cause:   
*Action:
select to_date('2012-feb-29','yyyy-mon-dd') + interval '3' year as dt from dual;
ORA-01839: date not valid for month specified
01839. 00000 -  "date not valid for month specified"
*Cause:   
*Action:
select to_date('2012-feb-29','yyyy-mon-dd') + interval '4' year as dt from dual;
29-FEB-16 00:00:00
select to_date('2012-feb-29','yyyy-mon-dd') + interval '1' day as dt from dual;
01-MAR-12 00:00:00
select to_date('2012-feb-29','yyyy-mon-dd') + interval '1' month as dt from dual;
29-MAR-12 00:00:00The problem exists in 10.2.0.4 and 11.2.0.3
Edited by: Sanjeev Chauhan on Feb 29, 2012 9:20 AM

Answer 1

>
considering this answered is simply sweeping an issue under the rug.
>
No - the question was answered. Did you read the reference that Paul cited? That is an ISO document and defines the standard.
The section he referred to is General Rules 3b and states:
>
b) Arithmetic is performed so as to maintain the integrity of the datetime data type that
is the result of the <datetime value expression>. This may involve carry from or to the
immediately next more significant <datetime field>. If the data type of the <datetime value
expression> is TIME, then arithmetic on the HOUR <datetime field> is undertaken modulo
24. If the <interval value expression> or <interval term> is a year-month interval, then the
DAY field of the result is the same as the DAY field of the <datetime term> or <datetime
value expression>.
c) If, after the preceding step, any <datetime field> of the result is outside the permissible
range of values for the field or the result is invalid based on the natural rules for dates and
times, then an exception condition is raised: data exception—datetime field overflow.
Note: For the permissible range of values for <datetime field>s, see Table 11, "Valid values for fields
in datetime items".
>
The relevant part of the above for year-month is
>
then the
DAY field of the result is the same as the DAY field of the <datetime term> or <datetime
value expression>.
>
DAY FIELD OF THE RESULT IS THE SAME AS THE DAY FIELD OF THE <DATETIME TERM>.
That is, for 'year-month' the day cannot change and, per section c, if it does an exception is raised.
That is how Oracle implements it. If the other databases implement it incorrectly then they have the problem not Oracle. The question was regarding Oracle's implementation so the question for Oracle is answered.
That document was printed in 1994 but the current document, ISO-8601 2004, does not alter it at all.
http://dotat.at/tmp/ISO_8601-2004_E.pdf