yesterday
last Sunday / month / week / year， the day before yesterday， the other day，once， in those days / years，once upon a time， earlier， this month /
week / year， then， sometimes， often， always， etc. Mary was here a moment ago.
过去常发生的动作或存在的状态，特征 He often went to Shanghai last year.
在虚拟语气中表现在/将来的情况 He talks as if he were my teacher.
在委婉用语中表现在/将来，常与could/would连用在时间，条件，让步等状语从句中表过去将来 I hoped you could help me.
They planned to go out if it was fine the next day.
一般将来时态 shall用于第一人称will用于各人称，表示将会意愿 tomorrow， in 2010， next morning / year / week / month / time， in turn， soon， before long， in the year， to come， from now on，one day， some day， from now on， sometime in the future， in a few hours / days， the day after tomorrow， this evening， this afternoon， etc. I shall do it tomorrow morning.
Shell have to go there by herself.
am/is/are going to+v.原表即将发生，打算做 It looks as if its going to rain.
is/am/are doing表计划，安排 Hes leaving for Guangdong tomorrow.
is/am/are about to+v.原表即将就要发生/做 She is about to go to school.
is/am/are to+v.原 表计划决定，要求，命令，传达命令指示等 You are to stay in the hotel.