converting seconds since epoch to time string

I have an integer column which holds a time represented
as the number of seconds since 1970/01/01 00:00 UTC. I want to
view this table with the time converted to an understandable text string.

I've experimented with things like

select to_char('epoch'::datetime + '973660200 seconds'::interval, 'dd/mm/yyyy hh:mi');
     to_char      
------------------
 07/11/2000 10:10 

but can't see anyway to use the time column in my table, instead of a hardcode
number of seconds.

In Sybase, you can use the dateadd() function to do this:

select dateadd( seconds, time, '1/1/70') from tablename

Thanks,
Bill