in表示“在某月(季节、年等)”如：in1996,inJanuary,insummer固定词组：inthemorning,inaweek,inaminute,intime,intheendon用于指具体的某一天或专指某一天上午、下午或晚上等.如：onChristmasDay,onthenightofFebruary16at用于具体时刻前和某些固定词组中.固定词组：atseven,atthemoment,atnight,atlast,atfirst,atnoon,attimes,atonce,atthistimeoftheyear,atthebeginningof,attheendofthismonth,atthesametime.注意：在表时间里,下列情况下一般不用介词.词组里有：next,last,this,that,tomorrow,yesterday,one,every,all以及thedaybeforeyesterday和thedayaftertomorrow前不用介词.如：不能说intomorrow,只能说tomorrow(在明天)