This idea floated into my head while listening to an enormous amount of people asking about the "hats" and what time they would arrive. To avoid confusion, I think it would be nice to have a "game clock", or a standardized clock based on the time zone of the Guild Wars server locations/hq/whatever. This clock could serve as a universal clock that everyone could follow and thus, eliminate any confusion as to when an event was occurring.
Also, this would be a VERY handy little gizmo for organizing Guild Events, such as GvGs, as I'm sure many of us have people in our guilds of whom are not in the same timezones as ourselves.
In terms of placement, I think it would be best suited in the Guild Window.
Sorry I wasn't more detailed, but how detailed can you really be about a clock anyway?