It is on WotCost official site : the weekend of 5 may 2018.
they wrote :
" Eternal Weekend returns in 2018, and with some big news—an expansion into Asia!
That's right! Eternal Weekends are coming! The first will take place in Paris, France, the weekend of May 5, as Europe's best Eternal players—and very likely some globetrotters as well—make their way to battle for the titles of Legacy and Vintage Champions.
The second Eternal Weekend takes place the weekend of August 18 in Yokohama, Japan, as the Legacy and Vintage Championships make their way to Japan for the very first time.
The third Eternal Weekend will take place in the United States, and we'll have more information available to you later this year on the location as those details are finalized. "