pgsql-bugs(at)postgresql(dot)org writes:
> In 7.0.3, I'm converting seconds from midnight to a time of
> day using interval ( 'seconds <val>'). This worked fine in
> 7.0.3 and gives a Bad interval external representation message
> in 7.1.
This has never been the intended or documented format; it should
be '<val> seconds'. Allowing both is ambiguous, so I'd say that
the behavior change is a correct one.
regards, tom lane