Is noon AM or PM?

Answer 1

The 12-hour clock is a timekeeping convention in which the 24 hours of the day are divided into two periods called ante meridiem (a.m., from Latin, meaning "before mid day", or "before the middle of the day") and post meridiem (p.m., "after mid day" or "after the middle of the day"). Each period consists of 12 hours numbered 12 (acting as zero), 1, 2, 3, 4,

The 12-hour clock can be traced back as far Mesopotamia and Ancient Egypt but may also have roots in Ancient India.[citation needed] However, the lengths of the ancient hours varied seasonally, always with 12 hours from sunrise to sunset and 12 hours from sunset to sunrise. In Egypt the hour beginning and ending each half-day (four hours each day) were considered twilight hours. An Egyptian sundial for daylight use[2] and an Egyptian water clock for nighttime use found in the tomb of Pharaoh Amenhotep I,[3] both dating to c. 1500 BC, divided these periods into 12 hours each.

The Romans also used a 12-hour clock: the day was divided into 12 equal hours (of, thus, varying length throughout the year) and the night was divided into three watches. The Romans numbered the morning hours originally in reverse. For example, "3 a.m." or "3 hours ante meridiem" meant "three hours before noon", compared to the modern meaning of "three hours after midnight".

The first mechanical clocks in the 14th century, if they had dials at all, showed all 24 hours, using the 24 hour analog dial, influenced by astronomers' familiarity with the astrolabe and sundial, and their desire to model the apparent motion of the sun. In Northern Europe, these dials generally used the 12 hour numbering scheme in Roman numerals, but showed both a.m. and p.m. periods in sequence. This is known as the Double-XII system, and can be seen on many surviving clock faces, such as those at Wells and Exeter. Elsewhere in Europe, particularly in Italy, numbering was more likely to be based on the 24 hour system (I to XXIV), reflecting the Italian style of counting the hours.
Exeter Cathedral clock, showing the Double-XII numbering scheme.
Exeter Cathedral clock, showing the Double-XII numbering scheme.

During the 15th and 16th centuries, the 12 hour analog dial and time system, with its simpler and more economical construction, gradually became established as standard throughout Northern Europe for general public use, with the 24 hour analog dial reserved for the more specialist applications, such as for astronomical clocks and chronometers.

Today, most analog clocks and watches use the 12-hour dial, on which the hour hand (shorter and sometimes thicker) rotates once every 12 hours, and twice in a day. Those are used even in cultures where the 24-hour notation is otherwise preferred. Some 12-hour dials show the numbers 13 to 23 written inside the primary 1 to 12 ring.

Although it has largely been replaced today by the 24-hour notation around the world, especially in written communication, the 12-hour notation with a.m. and p.m. suffixes is common in some parts of the world.
A typical analog 12-hour clock
A typical analog 12-hour clock

* The 12-hour clock is the dominant system of time written and spoken in:

* Australia
* Canada (except Quebec)
* New Zealand
* Philippines
* United States of America

* It is commonly used alongside the 24-hour clock in:

* Albania
* Brazil
* France
* Greece
* Quebec, Canada
* Turkey
* Ireland
* United Kingdom and other English-speaking regions
* some Spanish-speaking regions of South America

In many European countries, a 12-hour clock is commonly used in informal speech, but a.m. and p.m. are little known. If one wants to unambiguously refer to time in the 12-hour system, one uses descriptive phrases instead, such as in the morning, in the afternoon, in the evening, at night.

Abbreviations

The Latin abbreviations "a.m." and "p.m." (often written "am" and "pm"; "AM" and "PM"; and "A.M." and "P.M.") are used in English and Spanish. The equivalents in Albanian are "PD" and "MD", in Greek they are "πµ" and "µµ", and in Swedish (though in Sweden the 12-hour clock is nowadays rarely used) they are "f.m." and "e.m.". Most other languages lack formal abbreviations for "before noon" and "after noon" and their users use the 12-hour clock only verbally and informally.

[edit] Criticism and practical problems

For more details on this topic, see Comparison of the 12-hour and 24-hour clocks.

Many people who grew up with the 24-hour clock see the 12-hour notation as a less practical and outdated convention, especially in the context of written communication, computers and digital clocks. The arguments for or against a change to the more modern alternative are, in many ways, similar to the discussion on metrication. Even most people who grew up with the 12-hour clock, however, have problems indicating midnight and noon. Those who grew up with the 24-hour clock are also confused when they come across situations very common in, for example, Internet forums and email in which a message indicated as posted at "12:46 am" appears unintuitively and seemingly illogically before a message marked "11:05 am" for example.

The disadvantages most commonly voiced by critics in comparing the 12-hour notation to the 24-hour clock are:

* confusion about the correct notation for noon and midnight
* confusion about the difference between midnight at the start and end of a given date
* The rollover from 12 to 1 happens an hour later than the change between a.m. and p.m.
* The lexicographical order does not match the chronological order.
* It's generally more complicated to understand and to implement in software and digital electronics.
* Typographically, the a.m. and p.m. terms require more space.

[edit] Confusion at noon and midnight
Style Midnight
(start of day) Noon Midnight
(end of day)
24-hour clock, ISO 8601 00:00 12:00 24:00
Most digital 24-hour clocks 00:00 12:00 —
12-hour digital clocks with a.m. and p.m., e.g. in computers and consumer electronics 12:00 a.m.* 12:00 p.m.* —
American Heritage Dictionary 12 a.m. 12 p.m. —
U.S. Government Printing Office
Style Manual — 12 a.m. 12 p.m.
Antiquated 12:00 m.n.† 12:00 m. 12:00 m.n.†
Canadian Press
UK standard
NIST1 midnight† noon midnight†
NIST2 12:00 Midnight† 12:00 Noon 12:00 Midnight†
U.S. de facto legal 12:01 a.m. — 11:59 p.m.
* Digital clocks and computers appear to show the times 12 a.m. and 12 p.m., as in the chart to the right. While those phrases may be used practically, it helps to understand that any particular time is actually an instant. The "a.m." and "p.m." shown on the clock displays refer to the 12-hour periods following the instants of noon and midnight, not to those instants themselves. In other words, 11:59 a.m. shows until noon; at the instant of noon it flips to 12:00. Simultaneously, the a.m. flips to p.m., though, strictly speaking, neither a.m. nor p.m. applies to those instants of noon and midnight which separate a.m. and p.m.
† These standards are ambiguous with respect to midnight at the start and end of the day. The style guide writers who prescribe them did not say what their intention are with respect to the two midnights or to endpoint convention.

The terms ante meridiem (before noon) and post meridiem (after noon) do not apply literally to noon and midnight. Although meridies (literally midday) properly is noon, its abbreviation m. is not common.

In the United States, though, especially with the preponderance of digital clocks and computers since the 1980s, noon is often called 12:00 p.m. and midnight 12:00 a.m., as at the beginning of a day. With that convention, the change from a.m. to p.m. (and vice versa) coincides with the change of hour from 11 to 12. That is the American National Standards Institute (ANSI) standard.[citation needed]

The terms 12 a.m. and 12 p.m. are occasionally used in the UK, but with no consistent meaning, and such terms are generally considered to be ambiguous and incorrect, for reasons explained in the website of the National Maritime Museum, Greenwich:

To avoid confusion, the correct designation for twelve o'clock is 12 noon or 12 midnight. Alternatively, the twenty-four-hour-clock system may be used. The abbreviation a.m. stands for ante-meridiem (before the Sun has crossed the line) and p.m. for post-meridiem (after the Sun has crossed the line). At 12 noon the Sun is at its highest point in the sky and directly over the meridian. It is therefore neither "ante-" nor "post-".[4]

However, the sun is highest at noon, apparent solar time, not standard time. [5] (Apparent solar time is also known as local solar time.)

The use of 12:00 a.m. for midnight and 12:00 p.m. for noon is contrary to the U.S. Government Printing Office Style Manual[6] which recommends the opposite: 12 p.m. for midnight and 12 a.m. (formerly 12 m.) for noon.

But the American Heritage Dictionary (Second College Edition) says the opposite: Strictly speaking, 12 A.M. denotes midnight, and 12 P.M. denotes noon, but there is sufficient confusion over these uses to make it advisable to use 12 noon and 12 midnight where clarity is required.

Many U.S. style guides (including the NIST website) recommend that it is clearest if one refers to "noon" or "12:00 noon" and "midnight" or "12:00 midnight" (rather than to "12:00 p.m." and "12:00 a.m.", respectively). Some other style guides suggest "12:00 n" for noon and "12:00 m" for midnight,[7] but that conflicts with the older tradition of using "12:00 m" for noon (Latin meridies), and "12:00 mn" for midnight (Latin media nox).

The Canadian Press Stylebook (11th Edition, 1999, page 288) says, "write noon or midnight, not 12 noon or 12 midnight." Phrases such as 12 a.m. and 12 p.m. are not mentioned at all.

Still, the use of 12:00 midnight or midnight is problematic because it does not distinguish between the midnight at the start of a particular day and the midnight at its end. To avoid confusion and error, some U.S. style guides recommend either clarifying "midnight" with other context clues, or not referring to midnight at all. For an example of the latter, midnight is replaced with 11:59 p.m. for the end of a day or 12:01 a.m. for the start of the next day. That has become common in the United States in legal contracts and for airplane, bus, or train schedules, though some schedules use other conventions.

The 24-hour clock notation avoids all of those ambiguities by using 00:00 for midnight at the start of the day and 12:00 for noon. From 23:59:59 the time shifts (one second later) to 00:00:00, the beginning of the next day. Some variants of 24-hour notation (including the world standard ISO 8601) use 24:00 when referring to a midnight at the end of a day.

Endpoint convention

Endpoint is a term for the ends of an interval. Endpoint convention is whether the left endpoint (beginning), the right endpoint (end), both, or neither is included in the intervals; [8][9] In the case of the 12-hour clock endpoint convention refers to where midnight or noon are placed in the intervals a.m. and p.m. For example, if a.m. were to include midnight but not noon (left endpoint convention) then its interval in interval notation would be [midnight,noon). For most time intervals the left endpoint convention is used; for example, something is 49 years old until it is 50 years old, then is 50 years old for a year.

Advantages of the 12-hour clock

Main article: Comparison of the 12-hour and 24-hour clocks

Some notable advantages to the 12-hour clock:

* It corresponds to analog clocks, which almost all have just 12 hours.
* It makes distinct a.m. and p.m., while "11:00" with no suffix, as with the 24-hour clock, might be in the morning or evening if the clock being used is unknown. (However, that is caused paradoxically by the existence of 12-hour notation.)
* The use of a leading zero, as is often used for 00:00 to 09:59, is awkward to pronounce out loud. That pronunciation is common mostly in the US military, not in countries primarily using the 24-hour clock.
* The presence of fewer numbers on a clock face makes it simpler, particularly on a watch.
* The 1 to 12 chimes in a 12-hour clock tower are more practical then the 0 to 23 chimes or 1 to 24 chimes in a 24-hour clock tower.

Related conventions

Typography

The abbreviations "AM" and "PM" are variously written in small capitals ("am" and "pm"), uppercase letters ("AM" and "PM"), or lowercase letters ("am" and "pm"). Additionally, some styles use periods (full stops), especially in combination with lowercase letters (thus "a.m." and "p.m.").

The use of a.m. as written in the form of am, AM, or A.M. can be confusing because am is an English word, AM is an abbreviation for amplitude modulation and A.M. is an abbreviation for anno mundi, in the year of the world and for Master of Arts.

There are symbols for "a.m." (U+33C2 = "㏂") and "p.m." (U+33D8 = "㏘") in Unicode. However, they are meant to be used only with CJK fonts, as they take up exactly the same space as one Chinese character.

Stylebooks use a space between the number and the abbreviation a.m. or p.m. However, that is widely violated.

Informal pronunciation

In informal language it is common to round a time to the nearest five minutes and express the time as so many minutes past an hour (e.g., 5:05 is five past five) or minutes to an hour (e.g., 5:55 is five to six). The period 15 minutes is usually expressed as "quarter" (hence 5:15 is quarter past five) and 30 minutes is expressed as half (hence 5:30 is half past five or merely half five, the latter expression not being common in the U.S.A.).

The "half five" convention is sometimes used (for example, in Germany) to mean 4:30, i.e., "half-way to five".

Formal pronunciation

For accurate times, the minutes may be expressed as an exact number of minutes past the hour specifying the time of day (e.g., 6:32 p.m. is thirty-two minutes past six in the evening).

Times of day ending in ":00" minutes (full hours) may be pronounced in English as the numbered hour followed by o'clock (10:00 as ten o'clock, 2:00 as two o'clock). This may be followed by the "a.m." or "p.m." designator, though phrases such as in the morning, in the afternoon, in the evening, or at night more commonly follow analog-style terms such as o'clock, half past three, and quarter to four. O'clock itself may be omitted, telling a time as four a.m. or four p.m. Minutes ":01" to ":09" are usually pronounced as oh one to oh nine (aught one to aught nine may still be in use in some Commonwealth countries). Minutes ":10" to ":59" are pronounced as their usual number-words. For instance, 6:02 a.m. can be pronounced six oh two a m; 6:32 a.m. could be told as six thirty-two a m.

In contexts in which the speaker has recently mentioned the hour of the day or for some other reason believes it to be well known to his or her hearers, he or she may omit all reference to it and simply declare the minutes, using expressions such as seventeen minutes past the (top of the) hour [to refer to 4:17 am, or 11:17 pm, etc.] or three minutes till the bottom of the hour [which similarly signals the bottom half of the clock, such as 7:27 pm, or 9:27 am, etc.]. This is also true of television broadcasts whose signals are picked up in more than one time zone, since the hour varies with those zones.

U.S. Military pronunciation

Military circles use the 24-hour clock exclusively and would typically pronounce times ending in :00 minutes as the hour followed by "hundred" with an optional "hours" (as if there were 100 minutes in an hour). For instance, 16:00 would be pronounced "sixteen hundred" or "sixteen hundred hours". In many such circumstances leading zeros would be voiced. For instance, 08:00 may be said as: "Oh eight hundred (hours)."



Hope that helps ;-)

...Oh and in case it didn't for some reason, the answer is that noon is PM, midnight is AM

Answer 2

Think of it this way: Whatever minutes come after the 12 will take on the same am or pm as the 12 that they are associated with. So, if 12:07 am is clearly just after midnight, then THAT 12:00 is also "am" at midnight. Similarly if 12:02 pm is early afternoon, then THAT 12:00 is also "pm" at noon. Hope that helps to remember which is which.

Answer 3

AM is in the morning and PM is the noon

Answer 4

Definately PM

Answer 5

PM. It's the first hour of PM actually. Because the only other times it's 12 o clock is at midnight which is the AM.

Answer 6

Noon is PM. We had to deal with this recently in my 10-year-old daughter's Math. homework. Midnight is 12 AM.
I was never sure of this before!

Answer 7

If you think of a 24 hour clock midnight is 00:00 which is before 23:59 therefore midnight must be am if morning is before afternoon therefore noon must be PM.

Answer 8

Strictly speaking, AM means before noon (ante meridiem) and PM means after noon (post meridiem). Sticking to the literal definitions, noon itself is neither AM or PM.

Answer 9

noon is pm as the first twelve hours starts at 00:00 and after 12 hours it becomes pm(past midday)the next 12 hours is afternoon

Answer 10

PM. PM starts at12:00(noon) and ends at 11:59(minute before midnight). AM starts at 12:00(midnight) and ends at 11:59(minute before noon). don't think you are dumb for not knowing. TONS of people don't know the answer!!!

Answer 11

I don't know about noon, but for many years the military could not handle midnight. There could not be a time that was all zeros.
Everything that happened around then had to be logged as either 23:59:59 or as 00:00:01.