user: Question: What is the Date that has a Round of Semifinal?
Columns: ['Date', 'Venue', 'Opponents', 'Score', 'Round', 'Djurgården scorers', 'Attendance']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['2005-04-21', 'Grenadjärvallen', 'Rynninge', '3-1', 'Round 2', 'Larsen (2), Kuivasto', '1 276']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Round" = 'Semifinal';