I'll see you at five o'clock.
2. At：一天中的某个特殊点，如midday, noon等
The helicopter took off at midday and headed for the island.
What are you doing at the weekend?
At the New Year, millions of people travel home to be with their families (但是，在生日，必须使用 on your birthday).
We moved into this house on 25 October 1987.
I've got to go to London on Friday.
The office is closed on Fridays. (= every Friday)
What do you normally do on your birthday?
I'll come and see you in the morning for a cup of coffee, okay?
We usually go camping in July or August.
The house was built in 1835.
The garden is wonderful in the spring when all the flowers come out.
The population of Europe doubled in the nineteenth century.
He was such a clever musician. He could learn a song in about five minutes.
7. In a year's time / in two month's time，表示多长时间之后，某事会发生。
I won't say goodbye because we'll be seeing each other again in three days' time. （= in three days）
At + 公共节日和周末，但如果是某个特殊的一天或周末时，使用on
- We never go away at the New Year because the traffic is awful.（新年假日，一年的前最初几天）
- On New Year's Day, the whole family gets together. （新年的第一天这个特殊的一天里）
- I'll go and see my mother at the weekend if the weather's okay.（在周末一直这样）
- The festival is always held on the last weekend in July.（在7月的最后一个周末这个特殊的周末里）
In the morning/afternoon/evening，但是当指代某个特殊的早上时，使用in
- I always work best in the morning. I often get tired in the afternoon.
- The ship left the harbour on the morning of the ninth of November. (9月9日这一天的早上）
- In the evening they used to sit outside and watch the sun going down.
- It happened on a beautiful summer's evening. （在某个特殊的夏天的晚上）
in the night：某个特殊的晚上；at night：通常意义上的晚上。
- I was awake in the night, thinking about all the things that have happened.
- It's not safe to travel at night.
以each，every, next, last, some, this, that, one, any, all等词汇开头的时间短语，不需要使用任何时间介词。
- He plays football every Saturday.
- Are you free next Monday at two o’clock?
- Last summer we rented a villa in Portugal.