How do I get the current time in seconds in the unix epoch?

I have a function in PL/pgSQL which needs the current time in seconds
expressed as an int4. In 7.1 I was able to get this (I thought) with
date_part(''epoch'', timestamp ''now'') . That doesn't seem to work for me
in last week's -current.

Here's the PLpgSQL:
       v_seed := date_part(''epoch'', timestamp ''now'');

And here's the output:

NOTICE:  Error occurred while executing PL/pgSQL function
NOTICE:  line 4 at assignment
ERROR:  Timestamp with time zone units 'epoch' not recognized

What's the best way to do this?

Take care,

Bill