user: Question: When is the Monsters of Rock show with 12 bands?
Columns: ['Year', 'Date', 'Event', 'Days', 'Stages', 'Acts']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1990.0, '18 August', 'Monsters of Rock', '1 day', '1 stage', '5 bands']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Event" = 'Monsters of Rock' AND "Acts" = '12 bands';