When I was in IT in the US Midwest one of our clients was the government of New Zealand. 17 hours and also one day offset between them and us.
Made for a short shared work week and very few hours on those few days that both teams could be on the same conference call at decent working hours. And yes, date/time confusion was common until both sides got used to it. Then of course we each did DST changes on different dates in different directions. So cue fresh confusion and new offsets 4x/year. Such fun. Or at least such minor aggravation.
Maybe the Flat Earthers are on to something. If that made time zones go away I’m not so sure I’d be against adopting a Flat Earth.
Around the late 1960s, I read an article in “Boys Life” magazine by a kid whose father was the king of the island nation Tonga. The kid said that the IDL had previously been on the *west side of Tonga, but his father had had the international date line ‘bent’ around Tonga, that the IDL was now to the the east of Tonga.
This change made Tonga the first nation in the world to ring in the day, making possible their slogan, “Where Time Begins”.
*I think I got the directions right, correct me if not.
Ancient mariners using the Paris meridian instead of Greenwich is a plot point in Herge’s Adventures of Tintin - Red Rackham’s Treasure IIRC. Searching for a missing treasure in the wrong spot.
That’s where I first learned about the Paris meridian too! And the fact there was such a thing as latitude & longitude in the first place. My parents only ever bought me 4 issues of that comic, and that storyline continued through 2 or 3 of them.
Reading narratives from WWII written in Japan, one encounters December 8 as the day that Pearl Harbor was attacked.
And, of course, the Jules Verne character Phileas Fogg arrived in London misunderstanding the date as he had journeyed eastward. (A point Mad Magazine humorously treated with him disappearing as soon as he realized that point.)
According to Wikipedia the best (integer-numbered) meridian to use would be 169°W instead; it only intersects three small islands in the Bering Strait & Bering Sea, plus Antarctica. So if we wanted to optimize things in this way, the Prime Meridian should be about 11° further east.
Referring back to comments upthread, ISTM we could leave the Prime Meridian right where it is and move the IDL to 169W. Nothing very interesting or bad would happen except that a vast amount of software would need tweaking.
Bottom line: they don’t have to be 180 degrees apart from each other. The fact the actual IDL zigs and zags between about 150W & 160E at various points demonstrates that being 180 degrees offset from the Prime Meridian is as much a coincidence of geography and history as it is a necessary or even desirable feature of an IDL.
Where the IDL mostly needs to be is far from population centers to avoid date confusion between closely intercommunicating groups of people. And even that is actually not a “need”, more like a “very desirable want.”
The point being every bit of navigational and date handling code anywhere in anything would need to be scrubbed for any hidden assumptions that the IDL is in any way connected to 180E/W.
A bit like Y2K, assumptions like this can exist in a lot more places than just a few rather recently constructed libraries which themselves depend on the IANA file. Which file is not necessarily the sole universal source on this stuff.
I find glitches like that fascinating, but was it really a Date Line bug (and, if so, what weird format was used for internal timekeeping?), or a 180° = −180° bug?
No clue. I’m not specifically suggesting that the F-22 bug was IDL-related.
I was suggesting that unseen untested assumptions exist in every bit of software code. Whether it’s a payroll system, a fighter jet, or runs your $15 basic digital wristwatch. The only way we discover these unseen untested assumptions is audit for them ahead of time or run the experiment of making the change in the outside world then seeing what breaks.
The world could not prevent the calendar from rolling over from 1999 to 2000. So starting years earlier they audited what they could, fixed much of what they found, and braced themselves for a crash engagement with any unknown or as-yet-unfixed bugs on Dec 31 99.
That the latter step was pretty much a fizzle was largely mis-reported in the public press as saying the whole decade-long Y2K fire drill had been an expensive exercise in fear-based unnecessary work. Those of us in the industry back then knew that was far from the truth.
I’m just suggesting here and now that moving the IDL away from180E/W might well have some surprising consequences in practice areas surprisingly distant from ordinary timekeeping / calendaring.
It’s a fun thought experiment, since the odds on us moving the IDL to 169W are just about zero.
The whole concept behind the Prime Meridian is that longitude can be calculated by taking two reasonably accurate clocks on a ship. One is set to the time at some arbitrary known place and left alone, and the other is set to local noon every day via a sextant. By comparing the difference in time between the two clocks, you can tell how far east or west you are.
The British used London, specifically the Royal Observatory at Greenwich as that arbitrary place/time for setting their clocks. That’s why the reference time is Greenwich Mean Time (the local time), and it’s at the Prime Meridian (the arbitrary place), marked 0 degrees longitude.
(I’ve been to the Royal Observatory, and it’s all about timekeeping with respect to navigation).
In a previous life I was responsible for rewriting code that drew the grid lines on a live navigational map. Although we are used to navigating in terms of Lat/Long now, that is way short of a universal reality. Lat/Long has a whole range of disadvantages, mostly stemming from the fact that it is hard to make them play well with flat maps, and even harder to make them play well near the poles. There are a pair of pesky singularities that can and do wreck even the most carefully crafted code.
Two map systems that get a lot of use are the Universal Transverse Mercator and the Universal Polar Stereographic (which together are also used by most land military forces as the base of the Military Grid Reference System.) UTM/UPS project the Earth geoid onto a a set of planes, 10 degrees on a side (mostly), so that within each plane the map is two dimensional, and you can navigate in Cartesian coordinates, and do so in metres (very nearly). There are no singularities. The poles are no worse to navigate around than anywhere else. There is a small error is scale across each plane, but it generally doesn’t cause any issue.
The transformation from UTM/UPS to the geoid or Lat/Long is, well, messy. As the planes intersect it is generally allowed, for the sake of convenience, that a location near the boundary is allowed to appear in the coordinate space of all planes covering the intersection. So up to four planes. The anti-meridian is just plain evil. The number of edge and corner cases (literally) is ridiculous. The idea of trying to plot the international date line down this makes me queasy to think about.
One thing you learn really fast, quaternions are your friend.
Well, maybe not the most carefully constructed code. It’s possible to write code that deals gracefully with coordinate singularities. It’s just really, really hard, and hence really, really rare.
(aside: I’m still kind of proud of that project in my college Orbital Dynamics class, where I was one of only a couple of students whose code successfully navigated one such coordinate singularity. We were given a set of orbital elements and an uncertainty on each of them, plus a small number of high-precision measurements (not enough to completely determine the orbit from those alone), and had to refine the estimated orbital elements. The uncertainty given for the eccentricity was larger than the eccentricity itself, and in fact the correct answer corresponded to a “negative eccentricity”.)
I will grant that most navigational code expects input in Latitude and Longitude (except for @Francis_Vaughan 's code? So maybe not that universally), but even a singularity can be dealt with, and since there is none, if there is a problem navigating the non-existent singularity gracefully, it’s a bug in the code (we can also stipulate that bug-free code is really, really rare), like a poor choice of coordinates in the region of interest. You lose more F-22s that way…
My parents only ever bought me 4 issues of that comic, and that storyline continued through 2 or 3 of them.