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There is a sign outside a shop near us which says 'Parking for loading vehicles only from 7 to 12pm'. Does that mean between 7pm and midnight, or between 7am and noon?

For me 12.00 is neither post-meridian nor ante-meridian, it is either noon or midnight.

Equally when someone says from midnight on the 3rd, do they mean midnight which precedes the 3rd or midnight which ends the 3rd. The precise moment of midnight belongs neither to one day nor the other.

These are crucially important matters as regards flight timetables, and insurance policies. If the policy expires at midnight on the 15th, when exactly is that? It is why many insurance companies now speak of 12.01am on the 22nd or 11.59pm on the 21st.

Should it be insisted that all references to 12.00 state either noon or midnight and how can we express midnight with clarity?

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  • 12pm is generally noon. But omitting the am from 7am means that pm applies to that as well, so it's "loading only" from 7pm, all night to noon. That may indeed be what they mean.
    – Andrew Leach
    Nov 14, 2013 at 9:41
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    from 7 to 12pm is very likely from 07:00 to 12 noon
    – mplungjan
    Nov 14, 2013 at 9:42
  • Sounds plenty of room for confusion here unless people state 'noon' or midnight'. And to which day does 'midnight' belong? No one has even attempted that? And who are 'The American Heritage Dictionary of the English Language'? Does their writ run as far as my neighbourhood shopping parade in Berkshire, and will they pay if I get a ticket whilst following their rationale?
    – WS2
    Nov 14, 2013 at 9:49
  • very much related english.stackexchange.com/a/122325/44619 AKA everything you wanted to ask about "noon" but were too scared to ask :)
    – Mari-Lou A
    Nov 14, 2013 at 9:50
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    "only from 7 to 12pm" is VERY ambiguous and frankly irresponsible and lazy on behalf of that shop owner. Is it a "legally binding" sign (I can't think of the correct terminology) issued by the local authorities or Town Hall?
    – Mari-Lou A
    Nov 14, 2013 at 10:02

3 Answers 3

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12pm would be noon, i.e. midday or 12h00 instead of 24h00

According to wikipedia:

It is not always clear what times "12:00 a.m." and "12:00 p.m." denote. From the Latin words meridies (midday), ante (before) and post (after), the term ante meridiem (a.m.) means before midday and post meridiem (p.m.) means after midday. Since strictly speaking "noon" (midday) is neither before nor after itself, the terms a.m. and p.m. do not apply. However, since 12:01 p.m. is after noon, it is common to extend this usage for 12:00 p.m. to denote noon. That leaves 12:00 a.m. to be used for midnight at the beginning of the day, continuing to 12:01 a.m. that same day. The American Heritage Dictionary of the English Language has a usage note on this topic: "By convention, 12 AM denotes midnight and 12 PM denotes noon. Because of the potential for confusion, it is advisable to use 12 noon and 12 midnight."[16]

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  • Wikipaedia is all very well but I would not wish to rely on that if catching a flight from London to Melbourne which left at 12.00pm. You have also not answered the point about to which day 'midnight' belongs.
    – WS2
    Nov 14, 2013 at 9:44
  • If you read my quite you would have seen: The American Heritage Dictionary of the English Language has a usage note on this topic: "By convention, 12 AM denotes midnight and 12 PM denotes noon. Because of the potential for confusion, it is advisable to use 12 noon and 12 midnight."[16] Nov 14, 2013 at 10:08
  • @WS2 You are straying into legalese here, which is considered off-topic. We were well aware of the 12am / 12pm potential for confusion when I taught maths, and (in line with our exam board) insisted on the logical 12 noon/midday // 12 midnight. But we warned the pupils that they might encounter 12 pm, when it should by convention mean 12 noon, but might be being used wrongly. I agree that legalese should cite 23:59:59 or 00:00:01 to disambiguate 'midnight', but these are decisions that need to be taken by proper czars rather than grammar czars. Nov 14, 2013 at 12:10
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Midnight (or "0:00" in 24h notation) is the start of the day. If the policy ends at midnight on the 15th, it ends one minute before 12:01am.

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  • Who says? And would that be 12.01am on the 15th or 12.01am on the 16th?
    – WS2
    Nov 14, 2013 at 10:04
  • 12.01am of the 15th, because midnight is always the start (and not the end) of the day, but maybe that's just my European perspective. This is what NIST has to say about it: nist.gov/pml/div688/times.cfm In other words: it's ambigous.
    – Tim Jansen
    Nov 14, 2013 at 10:11
  • There is ambiguity all over the place here Tim. And have you noticed, that the more ambiguous things are, the more certain, and vituperative in their certainty, people become. But the link that Mari-Lou provides to an earlier post does clarify most of this very effectively indeed.
    – WS2
    Nov 14, 2013 at 10:20
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Let's consider the day starts at midnight (00:00) 12:00 a.m. Let's also consider we have it divided by two span of time (a.m/p.m) If the day starts at (00:00) 12:00 a.m., the 1st part will come to an end at 11:59, so the 2nd part starts at 12:00 p.m.

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