by the time+過去時(shí)間，主句過去完成。by the time+將來(lái)時(shí)間，主句將來(lái)完成時(shí)。

1)到...為止

如果從句中的謂語(yǔ)動(dòng)詞是一般過去時(shí)，那么主句中的謂語(yǔ)動(dòng)詞通常用過去完成時(shí)，表示“截止到從句動(dòng)作發(fā)生時(shí)，主句動(dòng)作已經(jīng)完成，即過去的過去”

He had left by the time we reached home.

當(dāng)我們到家的時(shí)候他已經(jīng)走了。

2.如果從句中的謂語(yǔ)動(dòng)詞為一般現(xiàn)在時(shí)/或現(xiàn)在完成時(shí)（表示將來(lái)），那么主句中的謂語(yǔ)動(dòng)詞常為將來(lái)完成時(shí)，表示“截止到將來(lái)某一時(shí)間為止，主句動(dòng)作將已經(jīng)完成”

By the time you get back，I shall have finished the work。

到你回來(lái)時(shí)，我將已經(jīng)把活做完了。

2)當(dāng)……的時(shí)候

如果只是說過去某個(gè)時(shí)候的狀況，用過去時(shí)，而不用完成時(shí)。

By the time we arrived the meeting was over.

我們到達(dá)時(shí)，會(huì)議已結(jié)束了。

By the time you get there the meeting will be over.

等你到了那里的時(shí)候，會(huì)議就該結(jié)束了。

By the time I arrived on the scene, it was all over.

我來(lái)到現(xiàn)場(chǎng)時(shí)，一切都已結(jié)束。

By the time this gets into print, they'll already have left the country.

這篇東西發(fā)表的時(shí)候，他們將已經(jīng)離開這個(gè)國(guó)家了。

She was tired and out of sorts by the time she arrived home.

她回到家里，又累又煩。

By the time we arrived, someone had grabbed all the good seats.

我們到達(dá)時(shí)，所有的好位子都給人占了。