One of the problems we have had for years in the Medway area is in compiling and maintaining a single, central calendar of all events going on in the area.
A few websites have tried to cover as much of this as they are able; but there is no formalised and structured mechanism in place to enable a single-point-of-contact reference source to be effecively and comprehensively established. Some event-promoting sites don't even have an RSS feed, which is all they need to enable to permit others to be aware of and read (and link to) their announcements and related posts.
I was speaking to someone who runs one of these "What's On" sites, for Medway, at Bloggle earlier this week, and he agreed that persuading those in this business whose sites are currently without an RSS feed should be encouraged to switch the facility on. Then, and only then, what is after all only fairly basic technology can raise the quality and completeness of "what's on" centralised publicity.
A common 'header' format might well be useful, containing dates/times/locations and the booking contact info (or 'none' if there is no need to book), but I'd tend not to make that
prescriptive, merely a suggestion or perhaps even a recommendation – but
I cannot think of any reason why anyone who is already making public the details of one or more events could have any objection to letting other sites add their promotional muscle and readerships. It's what I'd do if I were in that line of work myself.