父亲有时候会在星期天洗他的车.（提问“星期天”）
Father sometimes washes his car on Sunday. 陈述句
When does father sometimes wash his car?特殊疑问句,对“星期天”提问
父亲有时会在什么时候洗他的车?

不过DQ"Saturday"是提问星期六,句子没有星期六啊.