Hi,
I have made an extension called AllTimeZones [1] that lets anyone put up dates in a page in all Timezone formats. I think it will be especially useful for admins when announcing a meeting rather than the current usage I saw at http://meta.wikimedia.org/wiki/Wikidata/Events (using the Template:UTC with local time link) as I don't like the idea of opening a new website just to check my local time.
Reedy already suggested to make the zones in UTC format (I am still working at it), any other comments are most welcome. The UI really needs some work IMHO. You can see its screenshot at [2].
[1]http://www.mediawiki.org/wiki/Extension:AllTimeZones [2]https://github.com/nischayn22/AllTimeZones/raw/master/timezone.png