几点之前怎么说？

before xx o'clock

另外上午8点可以讲8:00am,下午8点可以讲8:00pm,依次类推,这是老外的常用法

before (2 oclock)
not late than (2 oclock)
by (2 oclock)

Before 8:00 AM(eight o'clock )在（早8点）之前。

before + time + am./pm.

before X:am or pm.

before + 时间

a few minutes earlier than + 时间