in,at,on,三者之间的区别.

表示时间的at,in,on：
at表示片刻的时间,如：at 8 o'clock ,常用词组有：at noon,at night,at midnight,at the end of,at that time,at the beginning of,at the age of,at Christmas,at New Year等.
in表示 一段的时间,如：in the morning,in the afternoon,in the evening,in October,in 1998,in summer,in the past,in the future等.
on总是跟日子有关,on Monday,on Christmas morning,on the following,on May Day,on a warm morning等.
表示地理位置的in,on ：in表示在某范围内,on指与什么毗邻,to指在某环境范围之外.如：Changchun is in the northeast of China./
Mongolia is on the north of China./
Japan is to the east of China.