When michele pirro is the pole position what is the date?
CREATE TABLE "race_calendar_and_results" (
  "round" real,
  "country" text,
  "circuit" text,
  "date" text,
  "pole_position" text,
  "fastest_lap" text,
  "winning_rider" text,
  "winning_team" text,
  "report" text
);
SELECT "date" FROM "race_calendar_and_results" WHERE "pole_position"='Michele Pirro';