What's wrong with my date/interval arithmetic?

Hi,

I ran this query on Postgres 7.3:

select min_time, max_time, min_time+age(max_time,min_time) as result,
to_timestamp('2003-10-17 23:07:00','YYYY-MM-dd HH24:MI:SS')
+age(to_timestamp('2003-12-01 03:50:45','YYYY-MM-dd HH24:MI:SS'),
to_timestamp('2003-10-17 23:07:00','YYYY-MM-dd HH24:MI:SS')) as expected_result from
(select min(postingblogdate) as min_time from blg_weblog_header) as min_time,
(select max(postingblogdate) as max_time from blg_weblog_header) as max_time

and get a result like this:
min_time,max_time,result,expected_result
2003-10-17 23:07:00,2003-12-01 03:50:45,2003-12-02 03:50:45,2003-12-01 03:50:45

Why is the "result" incorrect (off by one day)?
When I do the exactly same arithmetic using timestamps created
with to_timestamp, everything is OK ("expected_result").
Is this a bug or am I doing something worng?

thanks for any thoughts about this problem,
Wojtek

P.S. postingblogdate is of type "timestamp without time zone"