The CW has set dates for its annual DC/WBTV crossover. The three-night event kicks off with The Flash on at 8 PM Sunday, December 9, followed by Arrow on at 8 PM December 10 and capping off with Supergirl on December 11.

For this year’s crossover, The Flash and Supergirl will swap time slots. The Flash normally airs on Tuesdays and Supergirl on Sunday. Arrow airs in its regular Monday night slot. The crossover also will mark the first appearance of Batwoman (Ruby Rose).

At its upfront presentation in the spring, the CW president Mark Pedowitz said, “This is the first time ever that Batwoman make a live-action appearance on any screen.”

The Batwoman character began appearing in DC Comics stories beginning with Detective Comics #233 in 1956, in which she was introduced as a love interest for Batman. On TV, Batwoman first appeared in animated series Batman: The Brave and the Bold, which premiered on Cartoon Network in 2008. On film, Batwoman appeared in Batman: Mystery of the Batwoman, voiced by Kyra Sedgwick, a 2002 direct-to-video animated film based on animated series The New Batman Adventures. Batwoman also made a cameo in direct-to-video superhero film Batman vs. Robin and appeared in 2016’s Batman: Bad Blood, voiced by Yvonne Strahovski.