day 前何时用on何时用in
■崔长平 河南遂平一高（463100）
1 day 在指“具体某一天”时，其前使用介词on。
on Tuesday, on Christmas Day, on the 9th ,on one′s birthday, on New Year′s Eve 等等。
On the day he was killed, a speaker at a big meeting said,“Joe Hill is not dead! He will never die!”
On the way home my father told me of an incident that took place on his first day at school in Mr. Crossett′s class.
2 在有一个形容词或名词进行修饰时，且day又指“一天”时，其前使用介词on。
on a summer′s day
on a windy / rainy / snowy / cloudy / fine / cold / warm / quiet day
3 在指“某一段时间内的某些非连续的日子”的时候，其前使用介词on。
On warm winter days he may think that spring has arrived; he gets up and walks around.
On lovely spring days we used to go out for an outing with our schoolmates.
4 当day作“时候，时期，时代”解释时，其前使用介词in。
In those days people seldom did experiments to test their ideas.
In my day things were different.
In the days to come we shall all travel by air.
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