Nook Battle

Nook Battle is a cross-server event available in the ship in the city view.

Phases

 * 1) Sign-up: on 1:00 Wed - 2:00(GMT+0) Thu, the top 5 alliances in a server, with more than 150,000,000 Power can sign up. Only R1-R2 members from these alliances can sign-up the alliance.
 * 2) Join as an Individual: on 2:00 Tue - 00:00 (GMT+0) Fri, after the alliance signed up, alliance members (that have joined the alliance for more than 3 days) can sign up for the battle. R1-R2 alliance members decide who can fight in the event. Each alliance can send up to 30 members to the final phase.
 * 3) Match Time: When the rival is matched, participants will fight one of the matches during 11:50-15:10 (GMT+0). Each match lasts 30 min.

Source: Facebook Official F.A.Q.1005-Q4/1005-A4