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_81 (main_date VARCHAR, number_of_fixtures VARCHAR)
### Question:
What was the main date of the round with 20 fixtures?
### Answer:
SELECT main_date FROM table_name_81 WHERE number_of_fixtures = 20