介词 “in” 除了有 “在……里面” 的意思，它还可以作时间介词，表示 “在……期间” 或 “在……（时间）之内”。
 
文字稿
Hi, I'm Phil from BBC Learning English. Today, I'm going to tell you five ways to use in with time expressions.
Number one: months. I can say: I'm going on holiday in May.

Number two: seasons. So, we can say: In winter, it's cold.

Number three: years. So, I can say: I finished school in 2000.

Number four: most times of day. I leave home in the morning. I get home in the evening. But, I go to sleep at night. It's an exception!

Number five: We use it with in the past, in the present and in the future. In the future, you'll learn everything from videos.
 
用法总结
In is a preposition of time. It can be used with:
“In” 作时间介词时，可与以下类型的词语搭配使用：

1 in + 月份
I'm going on holiday in May.
I'll next see you at Christmas in December.
I think we arrived some time in June.
 
2 in + 季节
In winter, it's cold.
I think this year I'll have my holiday in summer.
Mummy, do the leaves fall off the tree in spring or in autumn?
 
3 in + 年份
I finished school in 2000.
The Titanic sank in 1912.
I grew up in the 1930s.
 
4 in + 一天的上午、下午和晚上
I leave home in the morning.
I'll see you in the afternoon.
I get home in the evening.
Be careful!
要注意！表示 “在夜里” 时，用介词 “at”。
I can't sleep at night.
 
5 in + 过去、现在、将来
In the past, people died much younger.
You need to learn to live in the present.
In the future, you'll learn everything from videos.