“Matches are still a week long, but have been split into two-hour time slices that we are calling skirmishes,” ArenaNet explained. “During a skirmish, players will earn war score normally as they always have, but war score is now being used to determine the winner of each skirmish. When each two-hour skirmish ends, war score is reset, but actual map state and objective status remains unchanged.”
The skirmishes will begin on September 9th in both North America and Europe. The studio said that the next phase will award more war score for various objectives, with future phases being determined on skirmish performance and feedback.
Source: Guild Wars 2. Thanks Leiloni!