I have a project I'm working on, and it involves knowing when the day starts.

If I were to pick a date, such as December 1, 2011.  Where on the world is the first place for December 1 to arrive? 

I'm staring at maps of time zones, and just having a helluva time figuring it out.  My first instinct was to say "Well, at UTC+12, of course!  The west side of the International Date Line.  New Zealand, the Marshall Islands, Fiji, those guys."  But there's Tonga, located on the west side of the IDL, but listed at UTC+13.  WTF?  How can it be 13 hours ahead of UTC, but still not in tomorrow?  Or yesterday?

Then there's the question of how many time zones are there?  Common sense says "12."  But there's Tonga, with its extra hour.  And there are a lot of countries or geographic areas (Australia, Burma, India, Afghanistan, Newfoundland, to name a few) that operate on the half-hour. 

So there it is.  Where does the day start?  And how many times does it start?

Ah, I didn't know that about Tonga.

Then the day hits first at Tonga, according to the timezone conventions. I'm guessing an exception was made for Tonga because it has to do buisiness with the rest of Polynesia on the other side of the IDL. The IDL doesn't follow 180deg. the way you'd think it should. It gerrymanders the same way the other time zone borders do to account for local convenience.

Astronomically, the day starts in the GMT + 12 timezone, though. Though GMT is astronomically arbitrary... as is any determination of where a given day starts first.

Then there's the question of how many time zones are there?  Common sense says "12." 

For starters, there are 24 Time Zones.  The occupants (humans) of the planet function on a 24 hour system and have divided the planet on which they exist into 24 zonal sections to represent the standardized time measurements used.

I do not know where Tonga considers itself in relation to the IDl, however, a quick Google produced this that may be helpful to you:  http://www.timeanddate.com/counters/firstnewyear.html

You guys are too smart for me.   

Sorry... 24, not 12.  Typo.

Growler67, that chart was exactly what I was looking for!  39 occurrences of a new day in a single 24 hour period.  Although Tonga does not appear on that list, so I'll have to figure out what to do about them.

Kooky. Samoa and American Samoa are at opposite ends of the chart...

I wonder if your question about "when the day starts" has anything to do with permissible hunting hours... when is sunrise and when is sunset?

I examined that question of "what time or date is it where?" quite a while ago and in looking at the maps, it appeared that many "aberrations" in the "International Date Line" as well as "Time Zones" were merely matters of mutually-agreed-upon practicality in terms of commerce and culture.

We humans built the time system for the world, and there is no external or cosmic authority to simply say, "The International Date Line is at exactly 180° of Longitude, like it or not, and go fly a kite if it happens to go through your living room."

As touched on above, there are even "islands" of areas on one side of 180° which actually consider their dates to be on the opposite side of the arbitrary 180° demarcation line.  This, once again, is dictated by commerce and culture and the choice of the inhabitants.



To illustrate this arbitrariness with an example slightly away from the "International Date Line" problem, I submit the following:

As it happens, Denver, at 105° West Longitude, is exactly on one of the "15° per hour" lines.  Yet, arbitrarily, without appeal to cosmic authority, it is the same time as it is in Denver for many miles in either direction from 105° W longitude:



You will note that even though there are 15° of the earth's rotation per solar hour (360° divided by 24 hours), up in the far northern reaches of Canada, this time zone runs from about 86° W to about 140° W, which amounts to about (140 - 86) = 54° of longitude.

This amounts, in turn, to 54°/15°(rotation per hour) = 3.6 hours total of solar time.  In other words, you can be as much as +/- 1.8 hours away from true solar time in those upper reaches of Canada.

Wow.

You will also note the rather glaring disjunct between the time zones for Edmonton, Alberta Province, Canada, and Winnepeg, Manitoba Province, Canada, compared to the corresponding United States time zones.  Hey, Albertans and Manitobans didn't like the way the US set it up.  So what can you do, sue them?

Well, whatever works for the inhabitants of that time zone.  It's all arbitrary anyhow.

After all, at the North and South poles, neither time zones nor the International Date Line have any meaning at all.  Lucky for penguins who are waiting for the 5 o'clock "happy hour,"eh?  It's "happy hour" all the time !  Woo-hoo !

Terry, 230RN

NOTE 1:  The map above is of course distorted in terms of mileage because it is a Mercator projection --as if the earth consisted of a cylinder rather than a globe.

NOTE 2:  I could not get the degree symbol, ° , to work properly in all cases.

What I'm wondering, in the most abbreviated version, is how many times could I legitimately celebrate the New Year in a 24 hour period.  The answer, at least so far, seems to be 39.

The answer, at least so far, seems to be 39.

What, in a really, really fast hydroplane or an aircraft?

Elaborate, please.

What kind of route would you be taking?  (See ETA below.)

New Years' celebrations at the stroke of midnight always seemed kind of silly to me anyhow, since it is only once in every four years that the new year actually starts near midnight. Three out of four years it's increments of about 6 hours away from the clock time until the next leap year.

Jeeze, I sound like Sheldon in "The Big Bang Theory" on TV, don't I?

So watch.  Somebody will stick that idea in a script and I won't get dime one for the idea.

Terry, 230RN

NOTE:  1 year = 365.242199 days as we reckon it by today's calendar.

ETA:  Hey, no fair changing your original post that much, Tom_G ! (Not that I haven't done it, too, but I am known to be etiquettally challenged!)

Quote

The answer, at least so far, seems to be 39.

What, in a really, really fast hydroplane or an aircraft?

Elaborate, please.

What kind of route would you be taking?  (See ETA below.)

New Years' celebrations at the stroke of midnight always seemed kind of silly to me anyhow, since it is only once in every four years that the new year actually starts near midnight. Three out of four years it's increments of about 6 hours away from the clock time until the next leap year.

Yeah, and the millennium turned over in 2001, not 2000.  You're over thinking this.

I want to throw a 24 (or possibly 25) hour party, starting with the very first occurrence of the new year at the IDL, and ending with the last occurance a day later.  And, every time the new year begins SOMEwhere on this planet, have a countdown and launch a new spread of snacks and drinks, appropriate to the region that's currently celebrating. 

Now, with some of these happening in 15-minute increments, that's not much time to indulge and imbibe, but this will be a party only for the seriously committed.  Plus, I'll have couches and nap mats.

Quote from: 230RN on November 26, 2011, 10:29:22 AM

Quote

The answer, at least so far, seems to be 39.

What, in a really, really fast hydroplane or an aircraft?

Elaborate, please.

What kind of route would you be taking?  (See ETA below.)

New Years' celebrations at the stroke of midnight always seemed kind of silly to me anyhow, since it is only once in every four years that the new year actually starts near midnight. Three out of four years it's increments of about 6 hours away from the clock time until the next leap year.

Yeah, and the millennium turned over in 2001, not 2000.  You're over thinking this.

I want to throw a 24 (or possibly 25) hour party, starting with the very first occurrence of the new year at the IDL, and ending with the last occurance a day later.  And, every time the new year begins SOMEwhere on this planet, have a countdown and launch a new spread of snacks and drinks, appropriate to the region that's currently celebrating. 

Now, with some of these happening in 15-minute increments, that's not much time to indulge and imbibe, but this will be a party only for the seriously committed.  Plus, I'll have couches and nap mats.

"couches and nap mats" lol! I think my mom still has the resting blanket she made me in kindergarten. Imma break that thing out next time I go home!

"You're over thinking this."

Nah.  My problems occur when I underthink things.  Actually, my responses were based on your original post, which you changed substantially, thereby changing the thrust of your question and the thrust of the thread title.

No problem, just a bit of a paradigm shift.  Don't get annoyed at me.

Terry, 230RN

"You're over thinking this."

Nah.  My problems occur when I underthink things.  Actually, my responses were based on your original post, which you changed substantially, thereby changing the thrust of your question and the thrust of the thread title.

No problem, just a bit of a paradigm shift.  Don't get annoyed at me.

Terry, 230RN

Annoyed?  Not in the least.  Although you have confused me. 

I don't see what I changed.  Initially I asked "Where does the day start?  And how many times does it start?"  I then refined it by saying the date I had in mind was Jan 1.  I don't see the paradigm shift.  Which is, really, not even a little bit important. 

Tom,

Go with GMT as a start. If you are going with a 24 hour division, it doesn't matter where you start, the earth is round.

Coming from someone who has been in every time zone on earth at least twice, a broken watch is right twice a day.


Bottle of wine should bring this into perspective.

-Chuck

Well, maybe I went a little overboard writing a tome about "Understanding Tome ZOnes & Int'l Date Lines."

It happens to be a subject (horology) of interest to me.

I just look at my Smart Phone, it knows what time it is no matter where I am(so far anyway).

No, the tower knows where it is and tells your phone.



(Just feeling feisty tonight.)