Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_2266976_1 (date VARCHAR, average_speed__mph_ VARCHAR)
### Question:
When was an average speed of 81.388 mph recorded?
### Answer:
SELECT date FROM table_2266976_1 WHERE average_speed__mph_ = "81.388"