[误] We got to the top of the mountain in daybreak.

　　[正] We got to the top of the mountain at day break.

　　[析] at用于具体时刻之前，如：sunrise， midday， noon， sunset， midnight， night.

　　[误] Don’t sleep at daytime

　　[正] Don’t sleep in daytime.

　　[析] in 要用于较长的一段时间之内，如：in the morning / afternoon， 或 in the week / month / year. 或 in spring / supper /autumn / winter等等。

　　[误] We visited the old man in Sunday afternoon.

　　[正] We visited the old man on Sunday afternoon.

　　[析] in the morning， in the afternoon 如果在这两个短语中加入任何修饰词其前面的介词都要改为on， 如：on a cold morning， on the morning of July 14th

　　[误] He became a writter at his twenties

　　[正] He became a writter in his twenties

　　[析]这句话应译为：他在20多岁时就成了作家。在某人的一段生活时间段中要用介词in来表示，而在具体岁数时用at来表示。

　　[误] He went to New York to find a job in sixteen years old.

　　[正] He went to New York to find a job at sixteen.

　　[析] 在具体年岁前用at， 如：at the age of 12， at your age，等等。

　　[误] We went to swim in the river in a very hot day.

　　[正] We went to swim in the river on a very hot day.

　　[析] 具体某一天要用介词on， 又如：on New Year‘s Day

　　[误] I’m looking forward to seeing you on Christmas.

　　[正] I’m looking for ward to seeing you at Christmas.

　　[析]在节日的当天用on，而全部节日期间用at，Christmas是圣诞节期间，一般要有两周或更长的时间。

　　[误] I haven’t see you during the summer holidays.

　　[正] I haven’t seen you since the beginning of the summer holidays.

　　[析] during表示在某一段时间之内，所以一般不与完成时搭配，如：I visited a lot of museums during the holiday. 而for表示一段时间，可以用于完成时，如：I haven‘t see you for a long time. 而through 用来表示时间时则为“整整，全部的时间”。如：It rained through the night.而since则是表达主句动作的起始时间，一般要与完成时连用。

　　[误] At entering the classroom， I heard the good news.

　　[正] On entering the classroom， I heard the good news.

　　[析] On 加动名词表示“一……就”。本句的译文应是：我一进入教室就听见这个好消息了。又如：on hearing… 一听见， on arrival 一到达就……(on表示动作的名词)

　　[误] In the beginning of the book， there are some interesting stories.

　　[正] At the beginning of the book， there are some interesting stories.

　　[析] at the begining与at the end都是指某事物的开始与结束部分，均不指时间范围，而in the beginning 则是指开始一段时间。in the end=at last是指“最终，终于”之意。

　　[误] Till the end of next week. I will have finished this work.

　　[正] By the end of next week. I will have finished this work.

　　[析] by 引起的时间状语表示了动作的截止点，其意思为“不迟于某一时刻将工作做完”，所以主句一般是完成时态。当然可以有将来时态，如：I‘ll be there by five o’clock.而till则表达其一动作一直持续到某一时刻，但句中的动词一定要用持续性动词，而瞬间的截止性动词应用其否定句式，如：I won‘t finish this work till(until) next weekend.

　　[误] He came to London before last weekend.

　　[正] He had come to London before last weekend.

　　[正] He came to London two weeks ago.

　　[析] before 一般要与完成时连用，而ago则与一般过去时连用。

　　[误] I have studied English for three years gince I had come here.

　　[正] I have studied English for three years since I came here.

　　[析] since用来表达主句动作的开始时间，所以其引出的从句中应为过去时，而不能用完成时态

　　[误] I can help you repair this bike. You will get it after two hours.

　　[正] I can help you repair this bike. You will get it in two hours.

　　[析]中文经常讲两小时之后来取，两天内会修好，而这个介词在英文中要用in而不要用after.其原因有二，①after 多用于过去时，如：I arrived in New York. After three days， I found a job in the bank. ② after 加时间是表达一个不确定的时间范围，如：after three days， 即三天之后的哪一天都可以。所以在许诺若干时间内会完成某事时，一定要用介词in.