A.m. and p.m.: What do they mean?

Folks, AM really means Ante Meridian and PM really means Post Meridian. It all has to do with the earth revolving on it axis and when the sun crosses the Prime Meridian on the earth. Times before the sun crosses the Meridian are 'Ante' or before and times after the sun crosses the Meridian are 'Post' or after. These concepts are all from basic Astronomy.

Well, considering such poor choices for alternative answers, the choice seems VERY obvious...

And just when I thought all the dumb people had posted, Amazing morning and time to work.

100 years ago, 100 monkeys were given 100 typewriters. In that time, they collaboratively managed to produce the selection of answers to this question. At least that's what I assume happened.

Eric Bittner Almost correct--but no cigar. NEWS FLASH: You're both wrong. The actual term in a.m. and p.m. is 'meridiem', not meridian. You'd think a "Professor of Chemistry and Physics" would know that... guess not. 

Ante=before, post=after. Diem=day, as in carpe diem. Meridiem=midday. Meridian is different. It's explaining a line which cuts the Earth in half; a midline

Almost correct. The meridian crossing is your local (or standard) meridian, not the Greenwich meridian, which defines local or standard noon.unless you're in the UK, in which case your description is correct.

It's not 0:00, it's 12:00 a.m.

24 hour time is the way to go. World Time. 0001 thru 2400. For afternoon times, simply add 12. Example: 3pm is 1500 hours.

Kind of explains it in the answer but fine to join in Jim Moser ,

Spc Kook Dude, cut and paste is only right if you cut and paste from the right source. Check the latin, it's meridiem when it modifies the time designation. If it modifies a task or described appointment, it would properly be used as a compound word with the "an" ending, as in "postmeridian duties". '

I wake up in the Early Morning A.M. feeling groggy from the previous night Excedrin P.M.

Meridians are circles of longitude. Meridiem is Latin for half day. You decide which words make more sense for a.m. and p.m. : half a circle of longitude or half a day

I had a job once, where I was taught that 12 noon was am and 12 midnight was pm, because 12 midnight correlates to 2400, the last hour of the day. Made sense to me, but the rest of the world (well, except for the IRS) doesn’t seem to see it that way. Since then, I have never written am or pm after the number 12. I always write, “12 N”, or “12 MN”.

Elma Griffiths, And I flunked it and French, as well! LOL Still graduated - Braintree, Mass. High School - class of 1949 - and I have survived to be 88 years old, so far.

Eric Fuller, l didn't know anyone but myself thought in those terms.

Wrong! I cut/paste all my answers so I am always right. read the question. The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin ante meridian, translating to before midday) and p.m. (from Latin post meridian translating to after midday). Each period consists of 12 hours numbered: 12 (acting as zero),1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11. The 24 hour/day cycle starts at 12 midnight (usually indicated as 12 a.m.), runs through 12 noon (usually indicated as 12 p.m.), and continues just before midnight at the end of the day. The 12-hour clock was developed from the middle of the second millennium BC to the 16th century AD. Learn ike I do from the internet. We always have he right answer. I've been insulted for being pompous but my boyfriend/fiance has told me that being narcissistic is one of my point. Join our blog since we are thinking about reality TV on our marriage vows. Stevie pays for everything and I can call myself as a kept man

After midnight and past midday was how I was taught in elementary school. Easier to remember I think.

Latin meaning should have been an answer option.

10/10 correct. Must be a genius. Nah, just know stuff.

Not correct answer but all wrong choices.

ante and post meridian