Inconsistent behavior with TIMESTAMP WITHOUT and epoch

Summary: "epoch" does not produce a consistent behavior when cast as
TIMESTAMP WITHOUT TIMEZONE
Severity: Annoyance
Tested On: 7.4.6, 8.0b4
Example:

test=> select extract(epoch from '2004-12-01 00:00'::TIMESTAMP WITHOUT TIME
ZONE);
date_part
------------
1101888000

this value is actually local time, not GMT time, as one might expect from
TIMESTAMP WITHOUT TIMEZONE. We see this problem when we try to reverse the
process:

test=> select timestamp without time zone 'epoch' + ( interval '1 second' *
1101888000 );
?column?
---------------------
2004-12-01 08:00:00

btw, to reenforce the above:

webmergers2=> select extract(epoch from '2004-12-01 00:00 GMT'::TIMESTAMPTZ);
date_part
------------
1101859200

thus, EXTRACT(epoch) as TIMESTAMP-NO-TZ produces local time, and CAST(epoch AS
timestamp-no-tz) produces GMT. This is inconsistent; it should do either
local time or GMT for both.

--Josh Berkus

P.S. if anyone is wondering why I'm doing epoch with timestamp-no-tz it's for
a calendaring application which exists on 2 servers in two different time
zones, and all I really want is the date.