user: Question: What is the Date of Tie no 21?
Columns: ['Tie no', 'Home team', 'Score', 'Away team', 'Date']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1', 'Blackpool', '0–1', 'Bournemouth', '7 January 1989']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Tie no" = '21';