https://www.gamespot.com/articles/fortnite-blitz-and-teams-of-20-modes-going-on-now-/1100-6459291/

Fortnite's 4.3 update has arrived, and along with introducing a new batch of content, it marks the start of a new limited-time mode in Battle Royale. This time, players have two special modes to choose from, Blitz v2 and Teams of 20 v2, both of which are now underway on PS4, Xbox One, PC, and iOS.

As their names imply, both events are new iterations of modes that have previously appeared in Fortnite, and they feature a handful of changes since the last time they were available. As before, Blitz v2 is a shorter match type, lasting a maximum of 15 minutes. Each round begins with the storm circle already closing in on the island, and the wait time between subsequent storms has been significantly shortened.