英语中作时间状语的短语前通常要加in, on, at, for等介词。例如： I get up at six o’clock in the morning. 我早上六点钟起床。 但在下列情况下，时间状语前不用介词： 1)当时间状语是today, tonight, yesterday, yesterday morning/ afternoon/ evening, tomorrow, tomorrow morning/ afternoon/evening等时。例如： There was a play yesterday afternoon.昨天下午有一场戏。 She will be back tomorrow morning.她明天上午回来。 2)由this, that ,these等构成的短语用作时间状语时，其前不用介词。例如： This term we are going to have a new subject.这学期我们将有一门新的课程。 He didn’t go home that night.那天晚上他没回家。 They are working on the farm these days. 这些天他们在农场工作。 3)由形容词last, next等修饰的名词词组用作时间状语时，其前不用介词。例如： I saw him in the street sometime last week.上星期我在街上看见过他。 Please come here earlier next time下次请早点来这儿。 4)由every, each等构成的短语用作时间状语时，其前不用介词。例如： Do you do morning exercises every day? 你们每天做早操吗？ They go to school by bike each day. 他们每天骑自行车去上学。 5)在以“the day(week, month, year)+before/ after„”构成的时间状语前不用介词。例如： Where did you go the day before yesterday? 前天你去哪了？ They came to this school the year before last. 他们是前年来到这所学校的。 6)在以all 构成的短语作时间状语时，如：all day, all the week, all the year 等前面通常不用介词。 例如： He was busy all day yesterday. 昨天他忙了一整天。 She was ill in bed all the week. 她有病了，卧床整整一个星期。 All that afternoon, I jumped and sang and did all kinds of things. 那天整个下午，我又唱又跳，各种各样的事都做了。 本文来源：https://www.wddqw.com/doc/52dfbdfa7c1cfad6195fa746.html