now() vs 'epoch'::timestamp

I've for some time used:

   (now()::timestamp without time zone - 'epoch'::timestamp without time zone)::reltime::integer

to get the current seconds since the epoch.  The results are consistant
with date +%s.

(Incidently, is there a better way in 9.4?)

But I found the 'epoch'::timestamp + $THAT_VALUE::reltime was off.

I consitantly get 1970-01-01 06:00 plus a fraction of a second from:

select now() -  ((now()::timestamp without time zone - 'epoch'::timestamp without time
zone)::reltime::integer)::reltime;

The machines on which I've tried it all have localtime == UTC.

Am I missing something obvious?

Also, is there any way to get the equiv of date +%s%N as a numeric or a
double precision?

-JimC
--
James Cloos <cloos@jhcloos.com>         OpenPGP: 0x997A9F17ED7DAEA6