Bunker is an event where you need to reach a point on the map and hold it until the timer runs out. It runs only on Vanilla+ servers — MR 19 and MR 25. There is no bunker on modded or any other servers.
All the details are in the in-game menu via /menu.
When: the exact schedule of the reworked bunker has not been announced yet — watch our socials and the in-game /menu.