difficulty formating interval datatypes in 7.4

Hello list,

I am working to format an interval in using the to_char() SQL function 
on postgresql 7.4.8.  I've had nothing but disapointment so far.
My confusion occurs when I'm trying to format using days where the days 
output would be more than 99.  For example:
I would like to do something like
     SELECT to_char('01-JAN-2001'::timestamp - '01-JAN-2000'::timestamp, 
'ddd "days" hh24 "hours"');
To get this
    '365 days 00 hours'
Currently I get this
    '335 days 00 hours'
I know that 'ddd' doesn't exist in the sense I'm thinking, but, it seems 
that either I've missed something or that to_char function wasn't 
designed with intervals in mind.  The 7.4 manual lists the following
"Warning: |to_char|(interval, text) is deprecated and should not be used 
in newly-written code. It will be removed in the next version."
But doesn't say what the alternative is.  Thanks for your help.

Chris M.