The following bug has been logged online:
Bug reference: 4718
Logged by: Roman Kononov
Email address: kononov(at)ftml(dot)net
PostgreSQL version: 8.3.7
Operating system: GNU/Linux x86_64
Description: "select +'8:00'::interval;" gives an error
Details:
test=# select +'8:00'::interval;
ERROR: operator does not exist: + interval
LINE 1: select +'8:00'::interval;
^
HINT: No operator matches the given name and argument type(s). You might
need to add explicit type casts.
test=# select -'8:00'::interval;
-08:00:00