Are you working in an Exchange environment?
If you are, you might find it easier to create a new Exchange user (say, call him "MarketingCalendar" (and, set the account to 'disabled'), and share 'his' calendar out.
(This is how I created a "Home Calendar" at home - it was the easiest way to create a calendar that everyone at home had access to, without creating weirdness with my own calendar.)
Just remembered that what I did was to create a "room calendar." That automagically sets the user account (that "owns" the calendar) to 'disabled', but leaves the calendar live.