This is incorrect:AM：after midnightPM：prior to midnightIt is:AM: ante meridiem (before noon)PM: post meridiem. (after noon)These words come from Latin (拉丁语)ante = prior to, beforepost = aftermeridiem = noonnote: 12 am = midnight, 12 pm = noonHowever it is often better to use midnight or noon to be clear in this case.In my high school English textbook it said that you could write 12 m for noon, however I have never seen it used.。