for+时间段 ,since+时间点 ,by+将来的时间 ,lately；recently, just,up to now, till now, so far, these days, in the past few years／months／weeks／days ,yesterday；last week；in 1945,at that time；once；during the war；before；a few days ago；when,used to+动词原形,be／become／get used to+动名词doing,before,after,by,up till ,will do.will be doing, have been doing
