in 后跟月份,季节,年,以及the morning ,the afternoon,the evening 这几个固定搭配. on 后跟日期,星期几,带day结尾的节日,that day,one's birthday,以及具体到某一天或有形容词修饰的morning,afternoon,evening （on the evening of Oct.1; on a windy morning) at 后跟具体时间（几点几分）,the moment,night,noon,早中晚餐,以及不带day结尾的节日.
