一般现在时:always, usually, often, sometimes, never
现在进行时:now, at the moment, right now
现在完成时:already, yet, just, ever, never, since, for
一般过去时:yesterday, last week, in 2000, two days ago
过去进行时:at this time yesterday, at 8 o'clock last night
过去完成时:by the time, before, after, by, until
一般将来时:tomorrow, next week, in the future, soon, will, shall
将来进行时:at this time tomorrow, at 8 o'clock tomorrow night
将来完成时:by tomorrow, by next week, by the time