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

### Instruction:
When is the Monsters of Rock show with 12 bands?

### Inputs:
table_name: table, columns: ['Year', 'Date', 'Event', 'Days', 'Stages', 'Acts']

### Response:
SELECT Date FROM table WHERE Event = monsters of rock AND Acts = 12 bands