Talk:International Date Line
From Academic Kids
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Getting the Adjustment Right
I was in the midst of an edit to be summarized as
- Copyedit the marvelous enhancement; move interlang link to top; add'l copyediting
and my edited text was to be
- The international date line is an imaginary line that for the most part is at ±180° Longitude, but has an odd shape to pass around Russia and islands in the Pacific. It is on the side of the Earth that lies opposite the prime meridian. Its purpose is to offset the hours that are added as one travels east through each successive time zone.
- The first phenomenon to occur in association with the date-line problem was part of Magellan's circumnavigation of the globe. The crew returned to a Spanish stopover on what had to be a Thursday, as attested by various carefully maintained sailing logs. Nevertheless, those on land insisted it was a Wednesday. Although readily understandable, this phenomenon caused great excitement at the time, to the extent that a special delegation was sent to the Pope to explain this oddity to him.
- Warning: Wikipedia contains spoilers
- The effect of ignoring the date line is also seen in Jules Verne's work of fiction Around the World in Eighty Days, in which the travellers return to London after a trip around the world, thinking that they have lost the bet that is the central premise of the story. Having circumnavigated in the direction opposite Magellan's, they believe the date there to be one day later than what it truly is.
- Anyone travelling west and passing the line must add a day to what they would otherwise expect the date and time to be. Correspondingly, those going east must subtract a day. Magellan's crew and Verne's travellers each neglected those adjustments, respectively.
However, i realized at that point that the marvelous account just added by the previous editor (which i touched up as above but treated as essentially accurate) has Magellan's crew (who travelled west) believing in a date that was too advanced, and needing to subtract a day (Thursday minus a day is Wednesday) to get right. I.e., needing to make the same adjustment i asserted Verne's characters did, despite travelling the opposite direction i asserted they did.
Marshalling the Evidence of a Mistake
- As you go west, you turn your clock back (make the time you believe in less) by an hour for every 15° of longitude, bcz the sun is not as far toward sunset as you would expect if you made no adjustment. Therefore you have turned back by 24 hours after 360° of westward travel, and to get even with people who didn't travel, you need to "turn your calender" forward (not back) by a day. If your count of days says it's Thursday, the lubbers will agree it's Friday, not Wednesday.
- According to Ferdinand Magellan#What else did they discover? at its last bullet point,
- That going round the earth westward was winning one day: upon their return they observed a mismatch of one day between their calendars and those who did not travel, even though they faithfully maintained their ship's log.
- "Winning a day" is ambiguous: is it analogous to your "gaining an hour's sleep" when you set the clock back in the fall, or to your clock's "gaining an hour" when you set it forward in the spring? Therefore not evidence either way. But possibly this source of confusion explains the contributor's making what i am calling an error: they misinterpreted "won a day", and assumed the wrong direction for the adjustment the article is describing.
- I'm a tad embarrassed to admit what the gut-level clincher for me is: i read Verne's story before i was 12 years old, and distinctly remember them landing in San Francisco, continuing east, and finding things getting easier as they got to the more technologized portions of the US, just before their last sea-travel to London. Eastward travel. And the plot falls apart if their calendar needs to be turned forward a day: they think they are a half day late, losing the bet, and it is by turning their calendar back that they realize they've won by a half day margin.
My version:
- traveling westbound, turn your clock backward when changing time zones, and your calendar forward when crossing the Line
- traveling eastbound, turn your clock forward when changing time zones, and your calendar backward when crossing the Line
(Unless i'm the confused one, maybe those two formulas belong side by side in the article!)
What to Do
I'm leaving this apparently erroneous version here, if only bcz i don't know how to fix it: assuming i'm right about the direction of the error,should it be
- "ship Wednesday, shore Thursday" (error was just reversing the days)
- "ship Tuesday, shore Wednesday" (error was in deducing ship date from shore one)
- "ship Thursday, shore Friday" (error was in deducing shore date from ship one)
- something else (one of the days was chosen at random as a mere example, or both days of week came from mistake in the tricky calculation from Zeller's congruence, or (unlikely, since Spain and Portugal made Julian-to-Gregorian shift while Columbus was at see) using the wrong calendar system.
And avoiding specific days of the week, but referring to the date given in the Magellan article. (I like the reference to days of the week, but let's get agreed about the direction of the correction, then about the days of the week, before putting that back in.)
As to the direction of the correction, i'm leaving my version of Verne as is, and making it vague as to Magellan: better to leave a possible old error in a little longer than to risk going back and forth; the info i'm removing has not been here long enuf for anyone to get used to it. --204.60.201.122 Jerzy 07:02, 14 Jan 2004 (UTC)
Kiribati days
I updated the number of days that Kirbati's government offices could communicate from three to four per week, as this chart will show is correct:
Asian side/American side Sunday/Saturday Monday/Sunday Tuesday/Monday Wednesday/Tuesday Thursday/Wednesday Friday/Thursday Saturday/Friday
There are four days where each is on a weekday.
Removed from article
"The Flora Commission, a special U.N. Commission under the direction of B. Joseph Flora of Fair Oaks, California, determined that this inefficiency could no longer be tolerated, as it would serve as an adverse precedent for attempts to increase government efficiency in developing countries." Sole contrib from an anon that I can't verify. Niteowlneils 03:21, 10 Dec 2004 (UTC)
