一般现在时 sometimes, often, usually, always, every..., on Monday/..., on
weedays,in spring/...,in the morning/...,等表示现在经常发生的动作的时间词。
一般过去时 last..., ...ago, yesterday等表示过去时间的短语。
一般将来时 next..., soon, in+段时间，tomorrow等表示将来的时间短语。
现在进行时 now, at the moment, right now, 还有动词 look, listen, 及句式，It's 6
o'clock, It's time for sth.
过去进行时 at eight o'clock yesterday, at this time yesterday, from one o'clock to
three o'clock yesterday, between one o'clock and three o'clock
yesterday, when/while 从句等表示过去的具体时间短语。
现在完成时 already,yet,ever,never, before, just. recently, these days,
in/during the past/last two years, how long 句式。
过去完成时 by the end of ..., 及表示过去的从句，如，before等，主句是过去时的
宾语从句。
过去将来时 主句是过去时的宾语从句中如表示将来的意思就用过去将来时。