Using custom date format in date_format_date()

hi,

i can't understand the way you could use custom date format defined in the admin UI.

ie : I've defined a custom date format 'xyz' with saying 'F Y' format string.

it's recorded in date_format_types table : Ok
but in date_formats it's tagged with custom type ???

what i need is something very simple :

print date_format_date($date_obj, 'xyz'); // that is currently not working