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Not a thread about daylight savings time
| November 2nd, 2015 at 5:11:52 AM permalink | |
| Pacomartin Member since: Oct 24, 2012 Threads: 1068 Posts: 12569 |
It's a consequence of a strong centralized government. China goes from 73°49′E to 134°45′E which is a change of over 60° in longitude. In the summer, for instance, it isn’t uncommon in Urumqi, Xinjiang's capital, to see people enjoying a beautiful sunset ... at midnight. Or for the sun to rise there in the winter around 10 AM. In order to accommodate people inconvenienced by the time zone change, shops and restaurants in Xinjiang often adjust their hours—but the effect can still be disorienting for the unaccustomed traveler. There were actually 5 time zones in the early part of the 20th century, but Mao unilaterally declared the country would observe one time zone in 1949.
Of course, and they have the clock to prove it now.  It did occur to me that when I said Paris and Madrid were using a time zone that was more sensible for Berlin that it is not just because Germany is the dominant economy in Europe. There was also a huge battle between locating the Prime Meridian in Paris or in London. Since Paris lost, it may want to be one time zone different than London just to show uniqueness. So despite being less than 3 degrees apart they are in different time zones.
Probably because Hawaii doesn't observe Daylight Savings Time. |
| November 2nd, 2015 at 5:15:37 AM permalink | |
| boymimbo Member since: Mar 25, 2013 Threads: 5 Posts: 732 | Trivia Time. Janet: What time is it for you? Mark: (replies) Janet: That's strange, it is the same time here. Janet is in Penascola, FL. It is 1:30 AM CST (they have fallen back) on November 1, 2015. Mark is in Jordan Valley, OR. It is 1:30AM MDT (they will fall back in 30 minutes) on November 1, 2015. Only the island of Newfoundland (not Labrador) is UTC -3:30, 30 minutes ahead of its friends in Labrador and the maritime provinces, but 90 minutes ahead of neighboring Quebec. |
| November 2nd, 2015 at 5:25:03 AM permalink | |
| boymimbo Member since: Mar 25, 2013 Threads: 5 Posts: 732 |
Hawaii moved from UTC -10:30 TO UTC -10 at 2:00am June 8, 1947 |
| November 2nd, 2015 at 5:52:39 AM permalink | |
| Wizard Administrator Member since: Oct 23, 2012 Threads: 239 Posts: 6095 | Janet is in Penascola, FL. It is 1:30 AM CST (they have fallen back) on November 1, 2015. Mark is in Jordan Valley, OR. It is 1:30AM MDT (they will fall back in 30 minutes) on November 1, 2015. Correct! Speaking of time -- the assignment for the advanced readers is to explain the Equation of Time.  Knowledge is Good -- Emil Faber |
| November 2nd, 2015 at 10:08:42 AM permalink | |
| odiousgambit Member since: Oct 28, 2012 Threads: 154 Posts: 5108 | An easy one until you get to why it would happen, the map gives it away. Part of Fl is central time, part of OR is mountain time. If the OR person was on DST and the FL not, they would have the same time on the clock. But why would this happen? I'm guessing they would be calling at the switch time for the FL person. The second trivia question looks like it has no easy part LOL I'm Still Standing, Yeah, Yeah, Yeah [it's an old guy chant for me] |
| November 2nd, 2015 at 10:13:52 AM permalink | |
| Fleastiff Member since: Oct 27, 2012 Threads: 62 Posts: 7831 | That would affect the HOUR not the HALF-HOUR. |
| November 2nd, 2015 at 10:30:09 AM permalink | |
| odiousgambit Member since: Oct 28, 2012 Threads: 154 Posts: 5108 | I assume we can't look it up. I am familiar with what I think you are getting at, the quandary, which is that someone using a sun dial does not get the same answer for the time of day that someone using official time does. Duck hunters notice one effect around January, btw, as more than a week goes by with the official time of sunrise hardly changing at all while the day is getting longer on the other end. The reason is that the Sun is altering its position, making that figure 8, by official time [of course all this is the Earth rotating and orbiting, the Sun is not doing it]. From pondering it, I believe it is due to the solstices not being timed exactly with the apogee and perigree of the elliptical orbit the Earth makes around the Sun. We humans are confounded since we want to make these concurrent in our heads. I believe if they were concurrent, we would not get the figure 8 [the analemma] After looking up "equation of time" in Wikipedia, I see someone says it is due to the obliquity of the ecliptic (the plane of the Earth's annual orbital motion around the Sun), which is inclined by about 23.44 degrees relative to the plane of the Earth's equator; and the eccentricity of the Earth's orbit around the Sun, which is about 0.0167. However, I now cannot tell you if I was right or not LOL. At least I am right in saying it is both the rotation and the orbit combined. I'm Still Standing, Yeah, Yeah, Yeah [it's an old guy chant for me] |
| November 3rd, 2015 at 8:26:25 AM permalink | |
| boymimbo Member since: Mar 25, 2013 Threads: 5 Posts: 732 | For the 2nd question there are two things at play. First, the length of the earth day is set constant at 24 hours which is the average of when the sun hits the zenith every day. If the earth was simply revolving and not orbiting the sun and not considering any other options the sun would be in the same place above your head at the same time every day. But the earth orbits the sun and when the earth rotates it takes a little more than one rotation for the sun to be above your head every day. The sidereal day is about 23 hours and 56 minutes and this represents the earth's rotation with respect to the stars. This is because the earth is orbiting the earth and the face of the earth has to move a little bit more to face the sun with the same angle. If the orbit about the sun were circular, this amount would be the same every day and the earth would be pointing at the sun in the same place every day. But because the orbit is an ellipse, the velocity of the earth relative to the sun changes according to Kepler's laws of motion. At the axis of the ellipse (early January and July) it is travelling slowest and the time of solar noon shift as the earth goes behind that average. For me this is more difficult to understand but it's the same concept except its the points above and below the elliptical of the orbit. Because the earth is above or below the celestial equator (the imaginary line where the earth's orbit would be if it were on axis) the difference above or below that orbit creates a difference in solar noon. |
| November 3rd, 2015 at 1:30:30 PM permalink | |
| odiousgambit Member since: Oct 28, 2012 Threads: 154 Posts: 5108 |
regarding your answers, I don't quite get why their are two parts to the question. Enough time, Michael, please "grade" our answers for the second trivia question. I'm particularly interested in your response to my comment "if they were concurrent, we would not get the figure 8 [the analemma]" I'm Still Standing, Yeah, Yeah, Yeah [it's an old guy chant for me] |
| November 9th, 2015 at 3:46:10 PM permalink | |
| Pacomartin Member since: Oct 24, 2012 Threads: 1068 Posts: 12569 | Hawaii is 155° W to 162° W. The natural center line for the 10th TZ to the west is 150° W and for the 11th is 165° W. sunrise to sunset in Los Angeles 7:12 AM-6:01PM (10:49:39) October 31 2015 UTC -7 6:12 AM-5:00 PM (10:47:47) Nov 1 2015 UTC -8 sunrise to sunset in Hawaii 6:34 AM-5:56PM (11:21:57) October 31 2015 (UTC -10) 6:34 AM-5:55 PM (11:20:54) Nov 1 2015 (UTC -10) sunrise to sunset in Hawaii (before 1947) 7:04 AM-6:26PM (11:21:57) October 31 2015 (UTC -10.5) 7:04 AM-6:25 PM (11:20:54) Nov 1 2015 (UTC -10.5)
I meant that even with the California switching from standard to daylight savings time, you would still have sunrise about the same time (just before or just after). Hawaii only experimented with DST for one year in the 1930's. As their day is always 12 hours give or take less than an hour, DST is kind of pointless. |