BUG #5050: text to timestamp failure

The following bug has been logged online:

Bug reference:      5050
Logged by:          Aoyai Kouhei
Email address:      aoyagi.kouhei@gmail.com
PostgreSQL version: 8.4.1
Operating system:   MacOS 10.6.1
Description:        text to timestamp failure
Details:

select '0001-01-01'::timestamp with time zone;
-> "0001-01-01 00:00:00+09:18:59"

...

select '1887-01-01'::timestamp with time zone;
-> "1887-01-01 00:00:00+09:18:59"

select '1888-01-01'::timestamp with time zone;
-> "1888-01-01 00:00:00+09"

select '1889-01-01'::timestamp with time zone;
-> "1889-01-01 00:00:00+09"

...