What is the date of Gavril Radomir's Bulgarian Victory?
CREATE TABLE "medieval_bulgarian_army" (
  "battle" text,
  "date" text,
  "bulgarian_commander" text,
  "byzantine_commander" text,
  "result" text
);
SELECT "date" FROM "medieval_bulgarian_army" WHERE "result"='bulgarian victory' AND "bulgarian_commander"='gavril radomir';