date/time problem in v6.5.3 and 7.0.0 ...

I can add days to now(), but not subtract? 

=====================================

template1=> select now() + '30 days';          ?column?           
------------------------------Sun Feb 13 22:00:33 2000 AST
(1 row)

template1=> select now() - '30 days';
ERROR:  Unable to identify an operator '-' for types 'timestamp' and 'unknown'       You will have to retype this query
usingan explicit cast
 
template1=> select version();                              version                               
---------------------------------------------------------------------PostgreSQL 7.0.0 on i386-unknown-freebsd4.0,
compiledby gcc 2.95.2
 
(1 row)




Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
Systems Administrator @ hub.org 
primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org