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_name_31 (date VARCHAR, competition VARCHAR, score VARCHAR)
### Question:
What was the date of the friendly competition with a score of 4-0?
### Answer:
SELECT date FROM table_name_31 WHERE competition = "friendly" AND score = "4-0"