age() function not to spec, date subtraction?

The age() function is documented as "Calculate time difference while
retaining year/month fields", but it doesn't seem to do anything different
from a plain date subtraction with a few time zone problems added in:

select age(date '1999-05-17', date '1957-06-13');
age
-------------------------------
41 years 11 mons 3 days 23:00
(1 row)

peter=# select age(date '1999-05-17', date '1999-06-13');
age
----------
-27 days
(1 row)

But then again, date subtraction has seen better days, too:

peter=# select date '1999-08-13' - date '1989-06-13';
?column?
----------
3713
(1 row)

peter=# select date '1999-08-13' - date '1999-06-13';
?column?
----------
61
(1 row)

As opposed to:

peter=# select timestamp '1999-08-13' - timestamp '1999-06-13';
?column?
----------
61 days
(1 row)

SQL sez date - date returns interval, btw.

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/