Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
On What Date is the Competition Semifinal that has a result of 2-1 aet?

### Inputs:
table_name: table, columns: ['Match', 'Date', 'Location', 'Lineup', 'Result', 'Competition']

### Response:
SELECT Date FROM table WHERE Competition = semifinal AND Result = 2-1 aet