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

### Instruction:
Which date has a Terrain of plain stage, and a Stage of 4?

### Inputs:
table_name: table, columns: ['Stage', 'Date', 'Route', 'Terrain', 'Length', 'Winner']

### Response:
SELECT Date FROM table WHERE Terrain = plain stage AND Stage = 4