a.m. or p.m. ???

[MustangLady]

hi. silly question from me (sorry to act so stupid) but is 12noon / 12midnight a.m. or p.m.
I was led to believe that 12noon would be am and 12 midnight would be p.m. Is that correct? There is a 'discussion' going on at the moment with couple of friends who all have different opinions about this. Which is it?

[Ethel]

Neither - am and pm mean post meridian and ante meridiem.

pm means 'after noon' and am is 'before' noon.

PM starts immediately after noon and am starts immediately after midnight.

http://wwp.greenwichmeantime.com/info/noon.htm

[Buenchico]

'a.m.' stands for 'ante meridiem' which is Latin for 'before noon'.

Similarly 'p.m.' (post meridiem) means 'after noon'.

So, strictly 12.00 noon can't be indicated by either a.m. or p.m. To stick with the Latin, it ought to be 12.00 m. (i.e. 12.00 meridiem)

However, there's a convention which accepts that, because 12.01 p.m., 12.02 p.m., etc, (through to 1259 p.m.) all indicate times in the hour commencing at noon, 12.00 noon may be indicated as 12.00 p.m., in order to maintain consistency. If this convention is accepted, it follows that 12.00 midnight, may be written as 12.00 a.m.

Chris

[Panic Button]

Industries that rely on accurate timing over the full 24 hour period such as airlines never refer to midnight. This is because it is hard to tell which you are referring to.

EG if I say midnight on Saturday do I mean midnight Fri/Sat or midnight Sat/Sun.

They therefore refer to 2359 or 0001, which identifies which end of the day you mean.

[almcd007]

I think it's common sense that one second after 12 noon (midday) it is PM and one second after 12 midnight is AM.

[Space]

12am is midnight
12pm is noon

[mibn2cweus]

All clocks that I have seen that indicate AM & PM go from:
11:59:59 PM in the evening to
12:00:00 AM at midnight
(those that indicate date, change to the next day at this time as well)

Conversly at noon they change from:
11:59:59 AM to
12:00:00 PM

[Hugh Spencer]

I agree with Space. It doesn't seem all that long ago when midday was 12 noon, not am or pm, and midnight . I prefer using the 24 hour clock when there is no doubt at all.

[Panic Button]

Sorry Hugh, but you therefore don't agree with Space

[kwicky]

Wouldn't life be a lot more convenient if we had a universal 24 hour time with all clocks throughout the world showing the same time.

[MustangLady]

Thank you all so much... believe it or not it now makes sense to me. I have now got to to concede to my friends that I was wrong, still --- we can't all be perfect!