The following bug has been logged online:

Bug reference: 1517
Logged by: Roy Badami
Email address: roy (AT) gnomon (DOT) org.uk
PostgreSQL version: 8.0.1
Operating system: Solaris 9
Description: SQL interval syntax is accepted by the parser, but the
interpretation is bogus
Details:

The parser accepts SQL interval syntax, but then silently ignores it,
treating it as a zero interval.

radius=# select date '2005-01-01' + interval '1' month;
?column?
---------------------
2005-01-01 00:00:00
(1 row)

radius=# select timestamp '2005-01-1 00:00:00' + interval '1' minute;
?column?
---------------------
2005-01-01 00:00:00
(1 row)

radius=#

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