The text for the Campaigns event starting today states:

"Campaign Period: TThursday, 11 May 2023, at 8:00 a.m. (GMT) / 9:00 a.m. (PDT) to Wednesday, 31 May, at 2:59 p.m. / 3:59 p.m. (BST)"

I think PDT is also meant to be BST (?)