Xfce config question

[Paul E Condon <pecondon@mesanetworks.net>]

I want to configure the clock display in Wheezy-Xfce to display
date and time of day combined and in an arrangement that is like
this
20120123 213703
i.e. 
YYYYMMDD HHMMSS

I had something this once before in the lower Panel, but I lost
it in a failed disk incident, and I can't remember where the
date/time display configuration is documented (and can't find just by
looking in there 'help'). I think I have found places where I can
type in format codes for date and time separately, but not together
in a single window, and I can't find a list of format codes from 
which to choose what to type.

Does anyone know? 

TIA

-- 
Paul E Condon           
pecondon@mesanetworks.net