BUG #6220: Flagstaff

The following bug has been logged online:

Bug reference: 6220
Logged by: Nicolas Beuzeboc
Email address: nicolasbeuzeboc(at)gmail(dot)com
PostgreSQL version: 8.4.8
Operating system: Ubuntu Natty
Description: Flagstaff
Details:

There is a month difference between the query results

it's not happening if I take the 7.4999.. number and multiply it by interval
'1 year'

psql (8.4.8)
Type "help" for help.

postgres=# select now() - interval '7.5 years', now()- interval
'7.4999999999999999 year', now() - interval '7.49999999999999999 years';
?column? | ?column? |
?column?
-------------------------------+-------------------------------+------------
-------------------
2004-03-23 11:44:30.980895-07 | 2004-04-23 11:44:30.980895-07 | 2004-03-23
11:44:30.980895-07
(1 row)

postgres=# select version();
version

----------------------------------------------------------------------------
----------------------------------------
PostgreSQL 8.4.8 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.5.real
(Ubuntu/Linaro 4.5.2-8ubuntu4) 4.5.2, 64-bit
(1 row)