When does the calendar change?

[fred rosenberger]

Ok, this came up in another forum, and it's something i've always wondered about.

My understanding is that the date changes at 12:00 midnight. so if i say "Wednesday at midnight", does that mean Wednesday is about to start, or Wednesday has just ended?

I always figured that it would mean that Wednesday is about to start. at midnight, it is no longer tuesday.

I think most people thinks the opposite way. they assume i mean "wait until wednesday night, and then at midnight...".

Does anybody have any thoughts or difinitive answers?

[i think this counts as pretty meaningless ]

[Mapraputa Is]

AM and PM start immediately after Midnight and Noon (Midday) respectively.

This means that 00:00 AM or 00:00 PM (or 12:00 AM and 12:00 PM) have no meaning.

Every day starts precisely at midnight and AM starts immediately after that point in time e.g. 00:00:01 AM

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

[fred rosenberger]

AM starts immediately after that point in time e.g. 00:00:01 AM

that's just dumb (IMHO). what about 00:00:00.5? 00:00:00.000000000007? i guess since (according to my limited understanding of quantum physics) time moves forward in discrete increments, there is some 'tick' from exactly midnight to the next, with nothing in between.

so i guess this means then that saying "Wednesday at Midnight" is ambiguous at best? or if the day starts at midnight, then the day is about to start?

or is this a stupid topic, and nobody cares but me??? (and maybe Mapraputa, but maybe she was just being nice)
[ September 09, 2004: Message edited by: fred rosenberger ]

[Helen Thomas]

Another example of Schrodinger's cat's dilemma, I think!

[John Smith]

i guess since (according to my limited understanding of quantum physics) time moves forward in discrete increments, there is some 'tick' from exactly midnight to the next, with nothing in between.

The time "tick" (year, hour, microsecond) exists only by convention. I don't think there is anything like a "quanta of time" in nature, representing the smallest possible chunk of time. That is, the time is continuous, not descrete, and all it is is a measure of change.

[Mapraputa Is]

AM starts immediately after that point in time e.g. 00:00:01 AM

Fred: that's just dumb (IMHO). what about 00:00:00.5? 00:00:00.000000000007?

"e.g." - Latin exempli gratia, for example.

Your examples are just as good. "immediately after" is a theoretical concept, and practically it depends on what kind of clock do you have.

so i guess this means then that saying "Wednesday at Midnight" is ambiguous at best?

[my first reaction corrected] Seem that you are right, and "Wednesday at Midnight" has no "official" definition. Which means if used, it should be checked that all involved parties agree on its meaning. For me, "Wednesday at Midnight" means that Wednesday just finished.

or is this a stupid topic, and nobody cares but me??? (and maybe Mapraputa, but maybe she was just being nice)

I just re-used a quote I used in another forum, where the question was when am becomes pm and vice versa.
[ September 09, 2004: Message edited by: Mapraputa Is ]

[fred rosenberger]

"at Midnight" means that Wednesday just about to finish.

why does it mean about to finish? if we agree that the 2 O'clock hour is the time from 2:00:00 until 2:59:59.999999, and i said "meet me at 2, wouldn't you show up when the hour was beginning, not ending?

Now, I agree that if Kathy had said "Thursday NIGHT at midnight", it would be crystal clear. And i don't mean to sound like i'm blaming anyone. I'm guilty of this sort of thing all the time.

Here's another interesting thing i don't understand... Today is the 9th of September, as i write this - a thursday. If i said "meet me next wednesday", would that be the 15th or the 22nd? i'm pretty sure most people would agree that i mean the 15th.

BUT... if i said to you "meet me next friday", would that be the 10th or the 17th? Here, i think most people would think 'the 17th'.

Why do we consider one to be 'the immediate one following', and the other to mean 'wait for one to come by, and THEN take the following one'?

[Mapraputa Is]

Ah, I see where it came from!

https://coderanch.com/t/94238/books/Isn-contest-closed

[Kathy Sierra]

Originally posted by fred rosenberger:
Now, I agree that if Kathy had said "Thursday NIGHT at midnight", it would be crystal clear. And i don't mean to sound like i'm blaming anyone.

Oh sure, you are SO blaming me...

But I agree, I should have said Thursday night, not just Thursday. It all seemed so clear in my little brain at the time... but now I realize that it indeed, as Helen said, was a Shroedinger's moment. So I am right here, right now, collapsing the waveform on what *I* meant... Thursday NIGHT, just as it is turning into Friday morning

cheers,
Kathy

[fred rosenberger]

Oh sure, you are SO blaming me

umm... well... errr... EDITORS!!! yeah - that's it. You're an author, right? so you have editors, right? so THEY should have caught that ambiguity.

See? it's easy to find someone else to blame!

I can't tell you the number of times i've started to post something here that made PERFECT SENSE in my brain, but as i start typing it, it quickly descends into the realms of chaos and random bits of nonsense, all seeming to be trying to convey some point.

On a good day, i'll read it and catch myself before hitting that "add Reply" button. the other 364 days of the year, i have to go back and re-edit my post 2, 3, or even 4 times, before i finally just delete my post in frustration.

Your post seemed to make sense to everyone but me... so now who's fault is it? And if i had actually thought about it, i would've figured out what you meant.

but i still would have argued about it, just for fun. My wife refers to me as the "pedantic literalist", or my other nickname, "Captain Literal".

[first edit to clarify things... sigh]
[ September 09, 2004: Message edited by: fred rosenberger ]

[Warren Dew]

Mapraputa Is:

This means that 00:00 AM or 00:00 PM (or 12:00 AM and 12:00 PM) have no meaning.

Whenever I've encountered them, 12:00 AM means midnight, and 12:00 PM means noon. Originally, this seemed counterintuitive to me, but I think the reason for it is that one wants 12:00 AM to be just before 12:01 AM, which is obviously just after midnight.

I agree with everyone that "midnight thursday" is ambiguous, and "midnight thursday night" is clear.

[Alan Wanwierd]

"midnight wednesday" is indeed ambiguous, but commonly understood without difficulty since most of us if we are to be up and about at that time of day would have approached it towards the end of wednesday - ergo midnight wednesday actually means midnight after wednesday night. (perhaps we shoudl call it "endnight" not "midnight"?

[fred rosenberger]

See, i guess i'm just hypersensitive to this sort of thing from when i worked for an airline. I can't tell you the number of times i got a phonecall from somebody who missed their red-eye flight because it departed a 1:07 am on tuesday, and without fail, they'd head to the airport tuesday evening... missing their flight by a good 24 hours.

And they'd blame us.

When i made these reservations, i always made a point of saying "this flight leaves at 1:12am on tuesday the 17th. That means you're going to head to the airport MONDAY NIGHT". 99% of the time, they'd come back with "Oh no! That's not what i wanted", and we'd have to rebook for the flight on wednesday.

Ever since then, i've been KEENLY aware of when the date changes, so i assumed am/pm worked the same way.