What was the day of vacancy for vitória de guimarães?
CREATE TABLE "managerial_changes" (
  "team" text,
  "outgoing_manage" text,
  "manner" text,
  "date_of_vacancy" text,
  "incoming_manager" text,
  "date_of_appointment" text
);
SELECT "date_of_vacancy" FROM "managerial_changes" WHERE "team"='vitória de guimarães';