Hi! Like Danzo said, the Arena 3 v 3 event will be opened until December 26th, 2018. The event opens every day during the event period for 4 hours each time at 10:00-14:00 and 18:00-22:00 server time. You still have time to collect some Chiriku fragments! The Arena 3 v 3 will be back again in the future =]