CREATE TABLE table_55684 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

When was the game at Essendon?
SELECT "Date" FROM table_55684 WHERE "Away team" = 'essendon'
SELECT "Date" FROM "table_55684" WHERE "Away team" = 'essendon'