Daylight Saving Time is set to begin in North America (http://www.timeanddate.com/time/change/usa) Sunday, March 12 at 2:00am Pacific Time. After this time change, all activity times like Sieges, Olympiad, Ceremony of Chaos, Dimensional Raid, Daily Vitality, and Instance resets will begin one hour later (server time).
No downtime is required for this change. If there are any questions about this change, please feel free to post them here. We also encourage you to follow @L2andAionOps (twitter.com/L2andAionOps) for maintenance and server status updates.