BUG #11031: Unexpected interval representations

The following bug has been logged on the website:

Bug reference: 11031
Logged by: Marius Bauer
Email address: marius(dot)bauer(at)here(dot)com
PostgreSQL version: 9.3.3
Operating system: Amazon RDS
Description:

Please see following query and result:

unitystg=> select a + b as sum, b - a as dif, 2 * a as pro, b / 2 as quo
from (select interval'1 day 15:45:25' as a, interval'2 days 12:34:56' as b)
as foo;
sum | dif | pro | quo
-----------------+-----------------+-----------------+----------------
3 days 28:20:21 | 1 day -03:10:29 | 2 days 31:30:50 | 1 day 06:17:28
(1 row)

Usually I'd expect the day will be adjusted in those cases when the hour is
>= 24 or < 0, but this does not happen.

The interval value itself is correct, just the representation is unexpected.