timezones BCE

Can someone help me understand

select '0101-01-01'::timestamptz;
timestamptz
------------------------
0101-01-01 00:00:00+00
(1 row)

test=# set timezone to 'America/Toronto';
SET
test=# select '0101-01-01'::timestamptz;
timestamptz
------------------------------
0101-01-01 00:00:00-05:17:32
(1 row)

select 'now()'::timestamptz;
timestamptz
-------------------------------
2022-04-13 12:31:57.271967-04
(1 row)

Specifically why the -05:17:32

Dave Cramer