The course ends at 4 PM.

The origin of the expression "at 4 PM" is based on the 24-hour time format, where the hours are numbered from 0 to 24. The expression "PM" stands for "post meridiem" in Latin, meaning "after noon".

Example sentences in Engpsh:

I have a meeting scheduled for 4 PM today.
The fpght departs at 4 PM sharp.

Example translations in Chinese:

我今天下午四点有一个会议。
这架飞机下午四点整出发。