'yyyy' for years prevailed....

Question

Hi ,
I have a generic question about date formats or just year format....
I know before the coming of the year 2000 , to solve the millenium bug, Oracle 'invented' the general format 'rrrr' for years or 'dd/mm/rrrr' for date format...which replaced the 'yyyy' and 'dd/mm/yyyy' for date formats respectively....
Why however , the 'yyyy' prevailed after the coming of 2000 year.....(I write prevailed because in the code examples ,at least, you posted in all Oracle forums , the 'yyyy' is exclusively used)????
Also , the use of 'yyyy' returns wrong results as the following examples.....
SQL> select to_date(sysdate,'dd/mm/rrrr')-to_date('10/10/1999','dd/mm/rrrr') from dual;
TO_DATE(SYSDATE,'DD/MM/RRRR')-
                          2630
SQL> select to_date(sysdate,'dd/mm/yyyy')-to_date('10/10/1999','dd/mm/yyyy') from dual;
TO_DATE(SYSDATE,'DD/MM/YYYY')-
                       -727857Thanks , a lot
Simon

Answer 1

Hi Nicolas,
very descriptive and 'instant' as always...!!!!!!!!!!!
Some points.....
1)The same results are displayed when setting the nls_format_date as 'DD/MM/RR';
2)SQL> select to_date(sysdate,'dd/mm/rrrr')-to_date('10/10/1999','dd/mm/rrrr') from dual;
TO_DATE(SYSDATE,'DD/MM/RRRR')-TO_DATE('10/10/1999','DD/MM/RRRR')
                                                            2630
SQL> select to_date(sysdate,'dd/mm/yyyy')-to_date('10/10/1999','dd/mm/yyyy') from dual;
TO_DATE(SYSDATE,'DD/MM/YYYY')-TO_DATE('10/10/1999','DD/MM/YYYY')
                                                         -727857
SQL> select sysdate "SYSDATE",
  2  to_char(to_date(sysdate,'DD/MM/RRRR'),'DD/MM/YYYY') "RRRR",
  3   to_char(to_date(sysdate,'DD/MM/YYYY'),'DD/MM/YYYY') "YYYY"
  4   from dual;
SYSDATE  RRRR       YYYY
22/12/06 22/12/2006 22/12/00063)>>and don't use a to_date on a date should help you
How then can i compute the number of days ...for example:
SQL> select '12/03/2004'-'15/01/2000' from dual; DOES NOT WORK.... using to_date works....!!!!!
4)Why do you all use the 'yyyy' and not real years 'rrrr' to return to my first post...????
Thanks , a lot
Simon