——cold winter nights前面是用in 还是用on?为什么?

——cold winter nights前面是用in 还是用on?为什么? 是in cold winter nights还是on cold winter nights ( ) a cold winter night.是用in还是on? 是in a cold winter 还是on a cold winter? last winter前面用in还是on还是at? 请问是In a cold winter morning 还是 on a cold winter morning? 是on a cold winter morning还是in? cold winter month前应加on还是in? （ ）a cold winter in还是on This story happened on a cold winter in 2007.请问这里用on对不对,为什么? on a cold winter day,还是in a cold cold winter day in the late afternoon和 on a cold winter morning为什么一个用in一个用on