in the 20th century, in the 1950s，
in 1989, in summer, in January,
in the morning/afternoon/evening/night,
in one's life, in one'thirties.
I will come and see you againin a week.
我一周后再来看你。(will come and see you again表示瞬时性的行为，故译为“一周后”)
She will learn another foreign language in three years.
她三年内将再学一门外语。(will learn another foreign language是继续行为)
She will get married in a year.
她一年后结婚。(get married是瞬时行为)
She will get married within a year.
她将在一年内结婚。(withinayear表示一年内)
2、on表示具体某一天及其早中、晚。
on May 1st, on Monday, on New Year's Day,
on a cold night in January, on a fine morning, on Sunday afternoon等。
注:如果某日某月在上(下)午之前有late,early等修饰语，介词仍用in。
in the late afternoon of 1st October 十月一日下午晚些时候
3、at表示某一时刻或较短暂的时间，或泛指圣诞节、复活节、年龄等
at 3:20, at this time of the year, at the beginning of..., at the end of...at the age of...,
at Christmas, at Easter, at Spring Festival, at dawn,
at dusk, at evening, at night,at noon, at this moment等.
注:在last,next,this,that,some,every等词之前一律不用介词。
We meet every day.我们每天相见。
4、in,after表示“在……之后的区别:
The bus will be here in ten minutes.
公共汽车10分钟后来这里。
She arrived after a week.
她在一星期后到达。
He will arrive after five o'clock.
他在五点以后到达。
5、from,since表示“自从......”的区别:
We work from Monday to /till/until/through Friday.
我们从星期一工作到星期五。
I haven't heard from him since last year.
我自去年以来未曾收到过他的信。
6、after,behind表示“在……之后的区别:
After two days our food gave out.
两天后我们的食物吃完了。
The plane was behind schedule.
飞机晚点了。
7、over, through, throughout均指“经过的全部时间”。
She stayed over the holidays.
她一直待到假期结束。
We stayed up through the night.
我们熬了一整夜。
It rained throughout the night.
雨下了一整夜。
8、for,since的区别
I have been there for six years.
我在那里已经待了6年了。
She has been learning English for ten years.
她已经学了10年英语。
We have not seen each other since 1993.
自从1993年以来，我们彼此未见过面。
9、during的用法:
He fell asleep during the lesson.
他在上课时睡着了。
She was born during the snowstorm.
她在暴风雪中出生了。
注:in和 during都表示一段时间，凡是能用in的地方，一般均可用 during，在这种用法上, during接近于in的意义。
She called on me during my absence.
我不在的时候她来拜访我。
You shouldn't call on his wife in his absence.
他不在的时候你不应去拜访他的妻子。
She was ill for a week, and during that week she ate little.
她病了一个星期，在那一周她吃得很少。
10、beyond表示“迟于;在…之后”之意。
beyond nine o'clock
过了九点
Some shops keep open beyond midnight.
有些商店营业到半夜以后。
11、through的用法:
On the eve of Christmas, young people usually stay up through the night.
圣诞节之夜，年轻人通常通宵不睡。
I could not dance, but I sat through the party.
我不会跳舞，但我耐着性子待到最后。
They are going to stay on themountains from Monday through Friday.
他们打算在山上从星期一呆到星期五。
注:此句中的 through是美国英语，英国英语一般用to或up to。它所指的时间包括其宾语所表示的时间在内即包括星期五在内。