On what date is there a score1 of 2 - 4 with the opponent Chelsea under 18s?
CREATE TABLE "stats" (
  "match" real,
  "date" text,
  "competition_or_tour" text,
  "ground" text,
  "opponent" text,
  "score1" text
);
SELECT "date" FROM "stats" WHERE "score1"='2 - 4' AND "opponent"='chelsea under 18s';