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Editorial Team
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Asked: 2026-05-19T15:18:14+00:00

I have a table that has the following data fromDate | toDate 20JAN11 |

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I have a table that has the following data

fromDate | toDate
20JAN11  | 29DEC30

Both dates are for the 21st Century (i.e. 2011 and 2030) but only the last two characters are stored.

Why is the following statement (when run from within a PL/SQL module) against the above data always returns a positive value 

dateDifference := (fromDate - toDate)

If i run the following statement from sqlplus i get the correct negative value which is correct. 

select to_date('20JAN11','DDMONYY')-to_Date('29DEC30','DDMONYY') from dual;

I remember reading somewhere that Oracle would sometimes use the wrong century but i dont quite remember the exact scenario where that would happen.

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1 Answer

  1. Editorial Team

    Assuming those columns are of DATE datatype, which seems to be the case: Oracle always stores DATE values in an internal format which includes the full year. The fact that you are seeing only a 2-digit year has to do with the date format used to convert the date to a string for display. So most likely the stored century values are not what you think they are.

    Try selecting the dates with an explicit format to see what you really have stored:

    SELECT TO_CHAR( fromDate, 'DD-MON-YYYY' ), TO_CHAR( toDate, 'DD-MON-YYYY' )
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