## is lunch time 12.00a.m or 12 .00pm ?

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oh the joys and nonsense of primary maths. ( i ve avoided several rants so far but this is amusing me ) . i know what i think , not necessarily this, its been avoided in the year 3 presentation but my 8 year old asked straight away and applied some pretty good logic to come up with his own answer  based on what we ve been working through so .......

lunch time (mid day ) 12.00pm ...... LIKE

lunch time (mid day ) 12.00am........DISLIKE

12 Noon.

12 a.m. and 12 p.m. are ambiguous and should not be used.

Better yet, be a rational human being and use a 24h clock instead.

Keith is right.  It is neither ante merīdiem (before midday) nor post merīdiem (after midday). It is midday, aka noon.  Similarly midnight is neither a.m. nor p.m.

But alas we have to put up with clocks which always display one or the other. So convention has lead to using p.m. for noon and a.m. for midnight. Probably because 11:59:59.99 is clearly a.m., and 12:00:00.1 is clearly p.m., and we usually truncate rather than round times.  So a clock could display the latter as 12:00p.m. and be technically correct I suppose, but an agenda should use 12 noon.

Another approach (which might be good for teaching) is to say the aim of writing down a time is to communicate it to someone. Since 12a.m. or 12p.m. are open to misinterpretation, they don't do a good job of communicating it and shouldn't be used at all.

Post edited at 11:48

One old style guide I have gives midnight as 12am and midday as 12pm but every other one I have had to use tell me to avoid am and pm in relation to the two liminal times. Midday or noon is preferable to 12pm and therefore midnight  or "in the morning" for 12am. Since the day used to start at sundown, 12 midnight was technically the morning of the next day.

I answered pm, but it's not really. It is the meridian. So it should be 12:00:00 m

The logic for pm is that the day starts at midnight, which is 12:00:00. Any time before that is the previous day. Hence it must be before the meridian at midnight.

If you are limited to am and pm, then the only other option is pm at midday.

https://en.wikipedia.org/wiki/12-hour_clock#Confusion_at_noon_and_midnight

To me, one second after* 23:59:59 is 00:00:00 (midnight) and the instant that the day starts. Twelve hours after 00:00:00 is 12:00:00, and so by symmetry that is the instant that the second half of the day starts. So:

23:59:59 = PM

00:00:00 = AM

11:59:59 = AM

12:00:00 = PM

23:59:59 = PM

etc

I write software for a living. A lot of the stuff I work on involves keeping tracking of the time that things happened, accounting for transitions to/from daylight savings time, etc. For computers, 00:00:00 is the first instant of the day and will be rendered as 00:00am in twelve-hour format.

* ignoring leap seconds and pedants

Post edited at 12:19

For a bonus point: has midnight on Monday already happened, or is it twelve hours in the future?

imco - In the future.

00.00.00 Monday is the middle of the night which started on Sunday dusk and ended at dawn on Monday. We call that "Sunday night".

I’m having lunch at Schrodinger’s.

It's a matter of infinitessimal approach: the actual point of 'noon' and 'midnight' are of zero duration (a bit like a stopped clock being precisely correct twice a day).

So go with convention: 12am is midnight, 12pm is noon. Or use a 24hr notation.

> I’m having lunch at Schrodinger’s.

or are you...?

> or are you...?

probably

You can have lunch but not at Schrodinger’s, or you can be at Schrodinger’s but not have lunch. You can't have both.

Neither. 12 o'clock when the sun is up is noon, the meridian.  Before that time it is am, ante meridian.  After that time, it is pm, post meridian.  12 am makes no sense, nor does 12 pm.  The 24 hour clock dispenses with this, but to avoid any possibly confusion over which day, the military has a convention in which midnight is 23:59.

Simply, lunchtime is 12 noon.

You're all wrong.

12:00 is 12 noon (neither am or pm)

but

lunch time is 12:30pm

It is definitely noon or 12 pm. If you think about it 12.00 doesn't exist, it is actually 12 plus some time ie you are 1 second (or whatever into the pm) 12 dead on is the completion of the previous twelve hours and is infinitely small.

> You're all wrong.

> 12:00 is 12 noon (neither am or pm)

> but

> lunch time is 12:30pm

That's all very well but your clock will say 12.00 pm (see my answer above)

> imco - In the future.

> 00.00.00 Monday is the middle of the night which started on Sunday dusk and ended at dawn on Monday. We call that "Sunday night".

I got caught out by this (as I'm sure plenty of other must have done too) with a UN job I was trying to apply for. It stated the deadline for applications was midnight on the 15th, and wouldn't let me submit an application an any time during the day on the 15th. They've since amended their deadline descriptions such that they expire at 11:59pm instead of midnight!

>  You can have lunch but not at Schrodinger’s, or you can be at Schrodinger’s but not have lunch. You can't have both.

That's lunch at the other fella's; at Schrodinger's you're served either your favouritest food or your least favourite, but won't know which until you get there

teach her 24 hour clock - avoid confusion

>  the night which started on Sunday dusk and ended at dawn on Monday. We call
> that "Sunday night".

Unless we have to get up before dawn, at which point we call it "oh god, why did I agree to  this on Sunday night"

Maybes aye, maybes naw

> lunch time is 12:30pm

Depends if work work night shifts or not...

> That's lunch at the other fella's; at Schrodinger's you're served either your favouritest food or your least favourite, but won't know which until you get there

Or poison...

Next question: Is zero an even or an odd number? My local council defines it as an even number for the purpose of deciding on the basis of your car number plate who is allowed to use the now-partially reopening recycling centres on which dates. Perhaps they have been thinking of the pickle that the Paris police/authorities got into on this issue over air-quality driven permissions to use a car on particular days.

> teach her 24 hour clock - avoid confusion

Not always. Believe it or not I was once issued a flight ticket timed e.g. "00.00 Tuesday 10 May" - which could've been midnight between Monday and Tuesday, or midnight between Tuesday and Wednesday - I had to ask the airline which it was - confusing and they shouldn't do that IMO, it should've been either 23.59 or 00.01

> Neither. 12 o'clock when the sun is up is noon, the meridian.  Before that time it is am, ante meridian.  After that time, it is pm, post meridian.  12 am makes no sense, nor does 12 pm.  The 24 hour clock dispenses with this, but to avoid any possibly confusion over which day, the military has a convention in which midnight is 23:59.

> Simply, lunchtime is 12 noon.

Exactly right. Took the words out of my mouth (or off the end of my finger). Nothing more to be said.

Should it be 00:00 or 24:00 at midnight - it is called a 24 hour clock 😁 - couldn't resist

> lunch time is 12:30pm

Only if you get up at a decent hour. Otherwise it's more like 1.30.

By convention, midday is called pm and midnight is called am.

On a similar time-related note, if your insurance expires at 00:00 and the new policy starts at 00:01 the same day, how long are you uninsured for?

> Only if you get up at a decent hour. Otherwise it's more like 1.30.

yes mine's been slipping till about 15:00 lately. Nearly tea-time!

Post edited at 14:29

> I’m having lunch at Schrodinger’s.

What time? Are you sure he'll be in?

Post edited at 14:43

Ultimately, it is an arbitrary choice. Nothing actually occurs bang on the division between yesterday and today, but given the finite precision of recording instruments or of the digital media in which those recordings are stored, things do so they have to be allocated to one day or half day or the other.

You get this issue whenever you are making measurements with finite precision of something that is continuous and then want to allocate these to bins of finite width. Should a measurement of 7.0 be put in the 6-7 or the 7-8 bin? It has to be in one, and can't be in both or in neither. For non-negative things it kind of depends on whether 0.0 has meaning and needs to be included in the 0-1 bin or excluded altogether.

I turned up for a "midnight" screening of a film, listed as being 00:00 on date X.

The cinema was all locked up.
They meant 00:00 on date (X+1)

I am not sure who was in the wrong.

It was only Suicide Squad anyway so I wasn't too upset.

To avoid that issue with my students when asking them to submit work electronically, and trying to be as generous as I can to them,  I always set deadlines to be 23:59 on the due date.

> Should a measurement of 7.0 be put in the 6-7 or the 7-8 bin?

Entirely subjective but I'd put it in the 6-7 bin, and I am always consistent with this sort of thing so at least I know !

> Should it be 00:00 or 24:00 at midnight - it is called a 24 hour clock 😁 - couldn't resist

Nice bit of lateral thinking, there.  This would also. I think, cope with the ambiguity of which day the midnight plane is actually leaving or of which day the midnight film is being shown. Personally, I think it's best to always go to bed well before midnight and then you can sleep through the problem period.

My mate Kev described a clock on a microwave oven which would go from 23:59 to 24:00 then to 00:01

> My mate Kev described a clock on a microwave oven which would go from 23:59 to 24:00 then to 00:01

What I want to know is who adjusts all the sundials when the clocks go back or forwards 1 hour A-HAH

> I got caught out by this (as I'm sure plenty of other must have done too) with a UN job I was trying to apply for. It stated the deadline for applications was midnight on the 15th, and wouldn't let me submit an application an any time during the day on the 15th. They've since amended their deadline descriptions such that they expire at 11:59pm instead of midnight!

I only made the mistake of using midnight as a deadline for a student assignment once.

Lunchtime topic of discussion at Schrodinger's: is zero a number?

thanks all.

8 year old decided 12.00 pm because he thought that as the clocked turned from 11.59.59 to 12.00,00 that was when the afternoon started (because the morning  had started at 00.00.00) .   it led us in to discussing the idea of  and need for a "convention" and has been said that  12 noon,12 midnight were better and that the 24 hour clock was  better still .  i also said that if we asked  a lot of people a small number would either not know or not agree with the convention and how this would cause confusion. i guessed that up to 20% of people  might disagree with convention. of course , i always think of ukc ers as smarter than the average cat.

edit : i meant not to use the phrase mid day in the original  post as we had already decided 12 mid day  was better and just say 12  lunch to be intentionally ambiguous. lunch time is of course 13.00.

Post edited at 16:20

That sounds hard. I'm off to the other fella's where if you pin me down to a risible answer you can't find me.

I didn't mean to bring Monty Python into this, honest.

Zero is regarded as even because it is a multiple of two.

https://en.wikipedia.org/wiki/Parity_of_zero

PM starts after any light has travelled far enough to complete a whole wavelength.  Or not as the case may be depending on the foam.

In your own frame of reference of course.

Post edited at 18:03

> lunch time is of course 13.00.

When I worked in Switzerland, it sometimes started as early as 11:30. That was at a university where even the lectures could start at 8. Before that, when I worked on a farm also in Switzerland, 11ses seemed to happen around 9, the day having started way before that. Since it involved something like brownies and something else that definitely was schnapps, I was OK with it.

I find it really fascinating that a simple question can rest on convention, practicality of measurement and on mathematical concepts - we haven't yet got to modular arithmetic.

> What I want to know is who adjusts all the sundials when the clocks go back or forwards 1 hour A-HAH

I believe its the Special Activities Division of the International Earth Rotation Service.

https://www.iers.org/IERS/EN/Service/IERSComponents/components.html

Its not a particularly well know organisation and - given how important it is that the earth keeps rotating -  I think they try to keep it that way. People who come into contact with their paramilitary branch tend to either lose their short term memory or just "disappear".

> PM starts after any light has travelled far enough to complete a whole wavelength.  Or not as the case may be depending on the foam.

> In your own frame of reference of course.

My frame of reference is a sphere less than a planck length in diameter, which has the useful property that lunchtime can be anytime I like.

it could therefore be lunchtime again as soon as lunch is over!   do you take bookings for your sphere?

> it could therefore be lunchtime again as soon as lunch is over!   do you take bookings for your sphere?

Trouble is, it's a tad small.

12 Noon does not work well, especially in the summer - noon is when the sun is at its zenith as measured locally, so approximately 13:00 in the summer if close to the meridian, later in the west and earlier in the east. How do we define mid-day? Not much better, most people would say 12:00 but 13:00 would be closer. When does morning end? Lunchtime solves all these problems! Good Lunchtime all...

Hi Pete, keeping well I hope.

Here's another complexity for all: Halachic ("ch" as in loch) midday (or 12:00 - take your pick). In religiously observant Judaism certain things have to be done before, at or after certain times (for example the afternoon service has to be in the afternoon - doh!). For this, daytime is divided into 12 equal parts and midday is half-way along those 12 parts ("hours"). Night-time is divided similarly.

Of course one of the complexities is that each day, the length of the day changes, so midday moves around between approx 12:00 and 13:00 throughout the year!!! A lot of the rabbinic discourse/arguments about this over the centuries has been to do with when does the day start? when does it end? how do you define nightfall? etc. which of course adds a further layer of possibilities.

Luckily, there aren't many halachic times in the day that need to be known, and there are 2 or 3 accepted definitions for start and end of a day (and the various religious groupings will follow one or other of those), and all the times have been worked out so you can just look them up, although of course you need to know your location because all of this is affected by your longitude (offset to local time) and latitude (length of day).

And some of you think "is midday 12am or 12pm" is complicated!!!

Post edited at 20:26

Hi Mike - yes, still keeping well. I had all my symptoms in the middle of December, before Covid-19 - maybe I got a sneak preview?

Anyway, Halachic calculation looks like something that could be done on a modern IQ capable Garmin - my Fenix6 knows sunrise/sunset times wherever it is in the world - but searching with Google has found no results. Maybe a chance to get back into programming?

Several religious websites do it, you just put your location in and done.

Gosh, literally just seen about John Allen, tragic. Were you still in touch with him?

> I write software for a living. A lot of the stuff I work on involves keeping tracking of the time that things happened, accounting for transitions to/from daylight savings time, etc. For computers, 00:00:00 is the first instant of the day and will be rendered as 00:00am in twelve-hour format.

For you, it's much easier then: everything should be seconds since 1970. ;-)

> For you, it's much easier then: everything should be seconds since 1970. ;-)

Yes. Although that just leaves the problem of what to do with events happening before 1970-01-01 00:00:00.

Oh and leap seconds.

And what time zone are the north and south poles at?

in your world presumably you can lunch at both poles at once?

Joking aside, managing date and time, together with localization, is probably where most time is lost in software development. Bloody nightmare. I wish everyone would just stick to UTC and English ;-)