at、in、on这三个时间介词也是我们初中英语学习的考点，时间介词的用法其实是有规律的。我们在生活当中安排自己的生活工作学习，一般都是以天为单位的，所以天就是时间介词的分界线。下面是时间介词用法注意事项，希望对学生学习时间介词知识有所帮助：
1."介词for + 表示时间的名词短语"表示动作持续或状态存在的时间段:
for ten seconds, for five minutes, for an hour, for two days, for six months, for a year, for a decade, for a whole century, for a long time, for a short while等。
例句1：On hearing the news, Helen stood there for ten seconds without saying a word. 听到这个消息后,海伦站在那里十秒钟没说出一句话来。
例句2：I feel as if I had left school for a whole century. 我觉得我好像离开学校整整一个世纪了。
2.不带介词的表示时间的短语:
just now, so far, last night, right away, the day after tomorrow, the day before yesterday, five days ago, five days before, this week, next week, a week ago, a week before, last month, next month, this year, next year, three months ago, this century, last century等。
例句1：The old couple haven’t heard from their son so far. 那对老夫妇目前还没收到儿子的来信。
例句2：Susan will take the college entrance examination the day after tomorrow. 苏姗后天要参加大学入学考试。
