" in + 一段時間 " 表[在一段時間之後],相當於[一段時間+later],亦可表[在一段時間之內],此時in相當於within.

例:

I'll be back in two minutes.

例:

In January 1981,in the wake of the Iran-Iraq War,oil giant Eroon announces that it would pour $11 billion into investment and exploration in overseas markets.

[在一段時間之內],此時in相當於within.

例:

I think I can finish the work in two minutes.

=I think I can finish the work within two minutes.

與日子並用  " on "

例:

John goes to church on Sunday.

例:

We're going to celebrate Leon's birthday on December 11.

注意:

in the morning/afternoon/evening

at night

on Monday morning

on Saturday night