What time was the kickoff when the miami dolphins were the opponent?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "kickoff_et" text,
  "opponent" text,
  "result" text,
  "record" text,
  "game_site" text,
  "nfl_com_recap" text
);
SELECT "kickoff_et" FROM "schedule" WHERE "opponent"='miami dolphins';