The current leagues will end at Feb 27, 2017 9:00 PM (this is displayed in your local time). At this time the realm will come down and we'll begin the process of merging your characters, items, masters, hideouts and Atlas progress to their parent leagues. When your stash tabs merge into the parent league, they stop being publicly listed on trade indexers. You can re-enable them in that league if you'd like. Any tabs with items in them that would exceed your stash tab allowance for the parent league become remove-only tabs.

What to Expect This Week
As per usual in the week leading up to the launch of a new league, we know that many Path of Exile fans are eagerly awaiting to receive information that will help them get a head start on being prepared.
While it's still subject to change, this week's news schedule looks as follows:
Tuesday (NZT): Legacy League Challenges
Wednesday (NZT): Content Update 2.6.0 Patch Notes
Thursday (NZT): Skill Tree and Item Filter Information
Friday (NZT): Two-day character slot sale information.
Saturday (NZT): Content Update 2.6.0 and the Legacy Challenge Leagues launch!