on
on表示具体某一天及其早、中、晚.
如on May 1st,on Monday,on New Year’s Day,on a cold night in January,on a fine morning,on Sunday afternoon等.
at表示某一时刻或较短暂的时间,或泛指节日等.
如at 3:20,at this time of year,at the beginning of,at the end of …,at the age of …,at Christmas,at night,at noon,at this moment等.
注意：在last,next,this,that,some,every 等词之前一律不用介词.如：We meet every day.
