What is the average year with an award of platinum?
CREATE TABLE table_66858 (
    "Year" real,
    "Date" text,
    "Title" text,
    "Format(s)" text,
    "Award description(s)" text,
    "Result(s)" text
)
SELECT AVG("Year") FROM table_66858 WHERE "Award description(s)" = 'platinum'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the average year with an award of platinum? ### Input: CREATE TABLE table_66858 (
    "Year" real,
    "Date" text,
    "Title" text,
    "Format(s)" text,
    "Award description(s)" text,
    "Result(s)" text
) ### Response: SELECT AVG("Year") FROM table_66858 WHERE "Award description(s)" = 'platinum'