Folks,
Trying to get the signal times sorted out in my head.
I see that today, Niku is Zulu (GMT) +13; was that the case in 1937 as well?
Entry 1 in the Post Loss Radio Signal Catalog (http://goo.gl/td1sm) gives Zulu 0006 July 3, Gardner 1306 July 2 (Zulu -11). Should this be July 3, which would make Gardner Zulu +13?
Entry 2 gives Zulu 0010 July 3, Gardner 1310 July 3, which seems like the correct offset (Gardner=Zulu+13).
Entry 3 is back to 0200 July 3, Gardner 1500 July 2 (Zulu -11)
Entries 4-15 continue with Gardner July 2; entry 16 is July 3; entries 17-21 go back to July 2; entry 22 is July 3; entries 23-43 are July 2.
Entry 42 gives Zulu 1115 July 2, Gardner 0015 July 2 for offset of Zulu -11, yet entry 43 gives Zulu 1119 July 3, Gardner 2319 July 2 for an offset of Zulu -12.
The remainder are for the most part Zulu -11.
GMT right now gives 4:08 a.m. Tuesday, and Niku gives 5:08 p.m. Tuesday, again for an offset of Zulu +13.
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I understand your confusion because I just checked the first three entries and they all have errors in the time conversions. Assuming that the Zulu time is correct then the Gardner time for the the first three entries should be 1206 July 2nd; 1210 July 2nd; and 1400 July 2nd. It is also possible that the Zulu times are not correct depending how they were arrived at, making an erroneous correction from local times. Just glancing at more of the listings at random, it appears that most of them use the
incorrect conversion from Zulu to Gardner time making Gardner time 11 hours slow on Zulu when the
correct difference for the standard time zone in which Gardner is located is
12 hours behind Zulu.
Standard time zones run from - 12 to +12 and are whole hours. For convenience, some areas may keep their clocks set to some other number and in 1937 Hawaii kept their clocks set to 10:30 behind on GMT but this was an exceptional case. There are other examples of this. No country set their clocks 13 hours ahead of Zulu until the year 1999 when the island nation of Kiribati, which includes Niku, decided to switch from 12 hours behind Zulu, which is the correct time zone for Niku, to 13 hours ahead of Zulu so that they would be the first country to enter the new millennium because the year 2000 would then arrive there prior to any other place on earth which they thought would bring in tourists. This is a completely new and non-standard way of keeping time and did not exist in 1937.
I posted the following message on August 29th: (the sign of the Zone Descriptions, Z.D., indicate the correction to local time to compute Zulu time and is the convention used by navigators and by the Navy and Coast Guard. I see by your posting that your use the opposite convention for the sign of the correction which is what you would use to compute local time starting from Zulu, hopefully this will not be too confusing for you. )
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Question:
"while thinking about the post loss messages. i considered a couple of things. what time would it have been on Nicu? at the times the message were recieved by dana on the fourth? and then when betty heard the other message."
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My response:
"That's kind of a nonsensical question. "Time" is a human construct so has no meaning on an uninhabited island since the land crabs do not wear watches. People choose whatever "time" is convenient for them. In the olden days every town kept its own time with towns further east seeing the sun rise before towns further west so their clocks were ahead and displayed a later time. With the arrival of railroads it became necessary to coordinate schedules across distances east and west so the concept of "zone time" was invented. Standard time zones are 15 ° wide because the sun travels 15° west every hour so this makes the "zone times" differ by exact hours. They extend 7.5 degrees (7° 30') each way from the standard meridians (which are spaced every 15° starting with the Greenwich Meridian) for that zone. This is the system used at sea but is often modified on land for convenience by not using the exact dividing lines between zones so that entire political units, such as states , can be on the same time and also some countries change their time to "daylight savings time" in the summer. So, for example, the standard meridian for the time in California is 120° west longitude and the zone extends from 112.5° (112° 30') to 127.5° (127° 30') west. To make it easy to convert from a zone time to GMT ("Z" time, or Zulu time) the zones are given numbers (called "Zone Descriptions, Z.D.) that you add to the zone time to find GMT. For California time it is + 8 so you add eight hours to California clocks to find Zulu time. (It changes for daylight savings time to + 7, but only in the U.S. It remains + 8 at sea.)
There is an exception in that there are two zones, each only 7.5° wide (7° 30'), abutting the 180th meridian. To the east the Z.D. is + 12 while to the west it is - 12 to account for the clocks saying the same time in each of these zones but the date being different. An example will make this clear. If you are at 174° 30'east longitude (west of the 180th, Z.D. - 12) on July 3rd and your clock says 2100 you subtract 12 hours and the GMT is 0900 on July 3rd. If you are at 174° 30' west longitude (on Gardner) (east of the 180th, Z.D. + 12) your clock also says 2100 but your calender says July 2nd. You add 12 hours and and find the same answer, 0900 the next day, July 3rd.
The clocks are set for convenience which is why the people on Howland kept their clocks set with a Z.D. of + 10:30 so as to keep the same time as that being kept in Hawaii for convenience of radio schedules. Hawaii was an exception and kept time with a Z.D. of + 10:30 because Hawaii is near the dividing line between two time zones and keeping time using either of those standard zones would cause their clocks to always be in disagreement with the sun, noon would never happen at 12:00 o'clock. Note, there was no such thing as "half-hour time zones," ships at sea at the same longitude of Hawaii kept their clocks set to the standard zone time with a Z.D. of + 10. (Hawaii now uses the standard time zone with Z.D. of + 10.)
U.S. Navy Regulation, Article 1031 issued in 1920 required Navy vessels to keep time based on the standard time zones. Paragraphs 6e and 8 however gave the commander the authority to set his clocks in a non-standard way (but he must note in the logbook the exact "hours, minutes and seconds" needed to convert ship's time to GMT as the Z.D.) when near a shore that kept non-standard time or under circumstances that "may render desirable a departure from the regular method." Itasca used this authority and kept time thirty minutes fast from the standard time zone for its location (+ 12), but Itasca was not keeping time in conformance non-existent "half hour time zones". A half hour zone would be 3.75 degrees (3° 45') wide so in such a system the + 12 hour zone would extend from 176.25° (176° 15') west longitude to the 180th meridian. If they had been using "half hour time zones" then both Howland and the Itasca would have been in the +12 "half hour zone" since they were at 176.6° (176° 38') west longitude, only 3.4° east of the 180th meridian. Itasca kept their clocks set to Z.D. + 11:30 for their own convenience (probably to keep their time exactly one hour different than Hawaii's to avoid confusion with radio schedules too.)
So what time was it on Gardner? Its longitude is 174.5° (174° 32') west so the Z.D. there is + 12 for that standard time zone and Earhart did not know that Itasca was using a Z.D. of + 11:30 so she would have had no reason to use that Z.D. But there is no reason to believe anybody on Gardner kept either of these zone times. If Earhart landed on Gardner then her time, the time on the cockpit clock, would be the same as Lae time, Z.D. -10, since her practice was to leave her clock set to the time at the departure airport. If Noonan looked at his chronometers then the time was GMT since his were set to GMT for navigational purposes."
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