在这句话里面的第一句Do not stay in the past 中，为什么用in？,不能用on呢？在常用时间介词中，in,on,at,for都是怎么用的呢？
at：在某个时间点,比如：at six o’clock.
in：（1）用在一段时间前，如：星期，月，季节，年；（2）泛指的“在上午/下午/晚上”即in the morning/afternoon/evening.但是泛指的noon, night 前加at.
on：在具体某一天，或某天的上午，下午，晚上，比如：on Monday morning/afternoon/evening/night.
for: 表示时间段。表示“计；达”，比如：They will stay here for a month.
during: 时间段，“在……期间”,during the winter/ performance
after: “在……之后” After the earthquake, everything was out of order.
by: “到……为止，到……” We had finished our work by last Friday.
before: “在……之前” Wash your hands before dinner.
until/till: “在……以前”；“到……为止” We worked until darkness.
from...to: “从……到……” Weekdays are from Monday to Friday.
曾经像个宝宝
二、时间介词in,on,at,for在用法上的区别_in _ spring , __in_ the evening, _in__ the middle of May, _in__ 2014 ,
__in__ his thirties, _in_ five hours, __in__ January, __in__ the 1990's,
__in__ / during the day
总结1：在月，四季，年，年代，世纪，泛指的在上午/下午/晚上时间短语里，以及其他表示较长时间的名词短语前，用介词in。
欢迎来到未来
_on_ Wednesday, _on_ Sundays, _on__ the morning of May 1st,
_on_ a cold night, _on_ a rainy afternoon, _on_ the fifth of July,
__on__ Christmas Day, __on__ Easter Day
总结2：在星期，具体某一天的上午/下午/晚上，以及节假日当天，用介词on.
_at_3 pm, _at_night, _at__ that moment , _at__ present,_at_Christmas Eve,
at Christmas,_at__breakfast/lunch, _at__midnight, _at_ the age of 12, _at_the beginning of the year
总结3：用在时间点、中午(noon)晚上(night)固定搭配里，以及节假日期间用介词at.
Learn from yesterday, live for today, hope for tomorrow. 借鉴昨天，活在今天，憧憬明天。
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。
总结4："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:。
