Half way to six from five, just like the ‘half’ in half past six is half way to seven 
A.M. and P.M. are abbreviations, but not acronyms, so if anything I would use <abbr>. Mind you, as others have said, these are standard abbreviations that don’t deserve extra markup.
I’m glad to hear that HTML 5 will support <abbr>, as it covers more bases.
Hm, Alex stole my thunder. I was going to say that, in Australia, ‘half six’ is three.
then once again, my dear friend, we will have to agree to disagree
and i resent how you’re always telling me that what i’m doing isn’t good policy
i certainly agree that semantic markup is important, but in this case, a.m. and p.m. are so well known that adding ABBR to them is silly
like somebody said, do it only “when it’s of genuine value to explain something that needs explaining”
Then you’re converting wrongly. The 12 isn’t added until you reach 1pm, i.e.1300hrs. 12:30p.m. is equivalent to, um, 1230hrs. 12:30a.m. is 0030hrs or 2430hrs, the second of which I’ve not seen used.
It’d be better if the US and UK would just catch up with the rest of the world
So true.
Hm, my analog wristwatch (an el cheapo from Walmart) has 24 hour markings. My first digital watch, from the 70s, and every one since, allowed the user to select a 12 or 24 hour display. For years, when I was an active ham radio operator, I had two 24hr clocks on the wall over my operating position; one set to GMT/Zulu time, the other set to local.
Not saying your backwards or anything but it seems rather strange to say that we’re the only users of the AM/PM system.
My experience is we’re in the minority, worldwide. In my personal world, almost everyone uses a.m./p.m.
cheers,
gary
I know. But those who doesn’t know this (which is the majority of the world’s population) will almost always do it as I wrote down above. Usually, this won’t matter much, as they’ll be able to figure it out anyway (it’s rare to meet with someone for lunch at 00:30 ), but for flight schedules etc. it’ll be quite important.
I’m not disagreeing with you Rudy at all, I just thought by the way you worded your post that you were against the use of marking up abbreviations in general. 
PS: When I was referring to clocks Christian I meant analog ones, they use 12 hours thereby making use of AM/PM
But besides that, the analog clock does not have the same inherent ambiguity problems that the a.m./p.m. system does.
I live in the Netherlands. We use ‘morning’ or ‘afternoon’ in speech or the 24 hour clock in writing.
As C. Ankerstjerne mentioned we also use ‘half six’ meaning 05:30
Peculiar, I could understand 29 minutes-to-six belonging to a six (in a perverse way) but not 05:30 becoming “half-six”. So what becomes of 23:30 “half-twelve” or “half-twenty-four hundred hours” leading to another day?
I live in the Netherlands. We use ‘morning’ or ‘afternoon’ in speech or the 24 hour clock in writing.
Yup.
You could get away with saying “8 uur 's ochtends” (morning) and “8 uur 's avonds” (evening) but if you don’t say the part of the day, then there’s a huge (12 whole hours) difference between “8 uur” and “20 uur”.
Peculiar, I could understand 29 minutes-to-six belonging to a six (in a perverse way) but not 05:30 becoming “half-six”. So what becomes of 23:30 “half-twelve” or “half-twenty-four hundred hours” leading to another day?
No, it’s half-twelve, but if it’s not really clear morning or evening you’re going to say evening.
It’s no different than you saying “quarter to 5” (we say “kwart vóór 5”) so if you would just say “half to 5” then you’d be like the rest of us, lawlz. Instead, you say “half past” which is just 6 of one or a half-dozen of another : )
Then you’re converting wrongly. The 12 isn’t added until you reach 1pm, i.e.1300hrs. 12:30p.m. is equivalent to, um, 1230hrs. 12:30a.m. is 0030hrs or 2430hrs, the second of which I’ve not seen used.
My clocks say 0 for midnight. But it can be called the 24th hour… I don’t think I’ve ever heard anyone say the zeroth hour, but then, lots of people just say “middernacht” (midnight). : )
Off Topic:
Precisely, and that is why 23:59 or 00:01 are the only sensible times you could quote to determine which day you are talking about (regarding 24:00 or 00:00) using 24-hour notation - so really it’s a 23-hour clock. 
What ever happened to 5:30 being “five thirty”? Works for us down here in Australia.
12:30 am and 12:30 pm are perfectly understandable.
Ralph, it’s worse than that:
42 is “two and forty” in Dutch : )
Heh heh, that’s how it used to be in English, too. I find that kind of lingo sorta cute, to be honest, and miss it a bit. “Four and twenty blackbirds baked in a pie…”
“four score and seven years ago…”
I forget how many fortnights make up a score, or how many hogsheads in a bushel, or how many farthings in a …whatever all that is.
Not at all. ISO 8601 is quite clear on that. 00:00 always falls at the beginning of the day, and 24:00 at the end of the day.
A score is 20.
As for the others, I had to Google:
How many bushels in 1 hogshead? The answer is 6.76751516692 (assuming conversion between bushel [US, dry] and hogshead [US]). O—K—(:
There were 960 farthings to the old British pound.
Not at all. ISO 8601 is quite clear on that. 00:00 always falls at the beginning of the day, and 24:00 at the end of the day.
…but… those are the same time??
I always figured time starting with 0 is like an array : )
Isn’t a hogshead a type of barrel? That would explain to me why in the Beatles song they have “and lastly through a hogshead of real fire” as then you would only need the cooper hoop and set it on fire and say it’s as wide as you’d need for a hogshead.
Is it a barrel large enough to contain a hog’s head? Poor hogs.
True. Basically, 2010-05-10T24:00:00Z is the same time as 2010-05-11T00:00:00. But since a specified time has a duration of 0, it’s not a problem (or, in other words(ish): 2010-05-10T24:00:00Z/2010-05-11T00:00:00Z = PY0M0D0TH0M0S0 ).
Ralph we also use “five thirty” in GB, I was just trying to comprehend the Dutch perspective of how Mickey Mouse’s hands could make it point so that it belonged squarely in the sixth hour.
Of course we also generally use the 24 hour clock for train timetables and that’s why typically 23:59 or 00:01 would make more sense.
Hmm, yeah…