ADV …点钟 You use o'clock after numbers from one to twelve to say what time it is. For example, if you say that it is 9 o'clock, you mean that it is nine hours after midnight or nine hours after midday.
The trouble began just after ten o'clock last night... 昨晚刚过10点钟麻烦就开始了。
I went to sleep, and at two o'clock in the morning I woke up. 我睡着了,凌晨两点的时候醒了过来。