WEBVTT - Is there an easy way to understand how time zones work? 0:00:00.520 --> 0:00:03.600 Welcome to brain Stuff from house stuff works dot com 0:00:03.600 --> 0:00:14.800 where smart happens. Hi Am Marshall Brain with today's question, 0:00:15.320 --> 0:00:19.440 is there an easy way to understand how time zones work? 0:00:20.440 --> 0:00:24.040 In January, people have a special interest in time zones. 0:00:24.360 --> 0:00:28.360 That's because the shouting of Happy New Year happens at 0:00:28.400 --> 0:00:33.200 midnight in your local time zone. Meanwhile, other time zones 0:00:33.360 --> 0:00:37.200 either have already celebrated the new year or they're sitting 0:00:37.240 --> 0:00:40.639 around waiting to do it. So cities in New Zealand 0:00:40.800 --> 0:00:46.440 celebrate New Year's Day first, followed by cities in Japan, Australia, Russia, China, 0:00:46.520 --> 0:00:50.280 and India, followed by cities in Europe and Africa, followed 0:00:50.320 --> 0:00:53.960 by cities in North and South America, and then ending 0:00:54.320 --> 0:00:57.440 on islands out in the Pacific Ocean like Hawaii and 0:00:57.480 --> 0:01:02.080 finally Samoa. There are four separate time zones, so there 0:01:02.120 --> 0:01:06.720 are twenty four separate times when balls drop, Happy New Year, 0:01:06.800 --> 0:01:11.240 gets shouted, and people engage in flagrant public displays of 0:01:11.240 --> 0:01:15.399 affection and intoxication. So let's start at the beginning. Why 0:01:15.400 --> 0:01:18.319 do we have time zones? Keep in mind that there's 0:01:18.360 --> 0:01:21.399 another way we could do this. We could have a 0:01:21.440 --> 0:01:24.560 single time that holds true all over the planet. When 0:01:24.600 --> 0:01:27.080 it's noon in Moscow, it could also be noon in London, 0:01:27.120 --> 0:01:30.120 New York, and Los Angeles. The problem is that people 0:01:30.280 --> 0:01:33.920 really don't like that. People much prefer for it to 0:01:34.000 --> 0:01:37.880 be noon when the sun reaches its peak in the sky. 0:01:38.040 --> 0:01:39.920 In order for it to be noon when the sun 0:01:39.959 --> 0:01:43.600 reaches its peak, everybody needs to set their time according 0:01:43.640 --> 0:01:46.560 to the sun. And this is how things used to be. 0:01:46.959 --> 0:01:49.600 It used to be that there were no clocks. People 0:01:49.680 --> 0:01:52.720 use things like sun dials. Then there were clocks, but 0:01:52.880 --> 0:01:55.720 only the rich people could afford them because they were 0:01:55.760 --> 0:01:58.880 really expensive. So a town would have a central clock 0:01:59.000 --> 0:02:02.400 tower with bells loud enough to be heard all over town, 0:02:02.520 --> 0:02:05.360 and the clock keeper would set the clock according to 0:02:05.360 --> 0:02:09.360 the sun. This system worked well until trains started to 0:02:09.400 --> 0:02:12.840 move quickly from town to town. In order to run 0:02:12.880 --> 0:02:16.440 a punctual train schedule, all the towns needed to have 0:02:16.520 --> 0:02:20.480 a coordinated time system rather than setting their clocks loosely 0:02:20.520 --> 0:02:24.080 according to the sun zenith. So the idea of time 0:02:24.200 --> 0:02:28.600 zones was created to help keep people from missing their trains. Today, 0:02:28.639 --> 0:02:31.040 the world has twenty four time zones, with all the 0:02:31.080 --> 0:02:34.440 clocks in the same time zone displaying the same time, 0:02:34.919 --> 0:02:37.880 but it can still be confusing, especially if you're trying 0:02:37.880 --> 0:02:41.160 to schedule a phone call with someone in China or Australia. 0:02:41.639 --> 0:02:44.720 How do you make sense of this? The easiest way 0:02:44.880 --> 0:02:47.280 is to get out a globe and a table lamp. 0:02:47.639 --> 0:02:51.520 The table lamp represents the sun position your globe, so 0:02:51.560 --> 0:02:55.160 that England is pointing toward the sun. In this model, 0:02:55.280 --> 0:02:59.640 it's now high noon in England. For historical reasons, the 0:02:59.760 --> 0:03:03.959 zero degree longitude line runs through Greenwich, England. This is 0:03:04.000 --> 0:03:07.120 called the prime meridian, and this place on the globe 0:03:07.160 --> 0:03:10.959 is also known as GMT plus zero or a Greenwich 0:03:11.000 --> 0:03:16.720 meantime or UTC plus zero, where UTC stands for coordinated 0:03:16.800 --> 0:03:21.079 Universal Time. So look at your globe looking down at 0:03:21.120 --> 0:03:24.519 the north pole. Imagine the globe divided into twenty four 0:03:24.639 --> 0:03:28.959 pie shaped slices. Each slice is a time zone. It's 0:03:29.080 --> 0:03:32.400 high noon in the England time zone. From the vantage 0:03:32.400 --> 0:03:36.320 point of the North Pole. The Earth spins counterclockwise. That's 0:03:36.320 --> 0:03:38.720 why the sun rises in the east and sets in 0:03:38.760 --> 0:03:43.080 the west. In the slice immediately adjacent to England on 0:03:43.160 --> 0:03:47.680 the left, it's one PM or UTC plus one. In 0:03:47.720 --> 0:03:51.360 the slice immediately adjacent to England on the right, it's 0:03:51.440 --> 0:03:57.400 eleven am or UTC minus one. As the Earth rotates counterclockwise. 0:03:57.760 --> 0:04:00.680 In one hour, it will become high noon in the 0:04:00.720 --> 0:04:05.680 slice immediately adjacent to England on the right. Five hours 0:04:05.720 --> 0:04:07.960 after its high noon in England, the Earth will have 0:04:08.080 --> 0:04:10.600 rotated enough for it to be high noon on the 0:04:10.640 --> 0:04:13.800 East coast of the United States. This is referred to 0:04:13.960 --> 0:04:17.680 as U t C minus five. The central time zone 0:04:17.680 --> 0:04:20.640 of the U S is ut C minus six, Mountain 0:04:20.680 --> 0:04:23.719 and Pacific are U t C minus seven and UTC 0:04:23.920 --> 0:04:28.240 minus eight, respectively. Hawaii is U t C minus ten, 0:04:28.440 --> 0:04:32.000 and finally Samoa is U t C minus eleven. The 0:04:32.080 --> 0:04:35.320 International date Line is on the opposite side of the 0:04:35.360 --> 0:04:39.360 globe from England, over near New Zealand. This first time 0:04:39.480 --> 0:04:43.440 zone is ut C plus twelve. This is the first 0:04:43.520 --> 0:04:47.680 time zone to see January one. Each new day starts 0:04:47.960 --> 0:04:51.239 in the time zone adjacent to the International date Line 0:04:51.760 --> 0:04:56.440 twelve hours before it's midnight in England, it's midnight in Auckland, 0:04:56.480 --> 0:05:00.080 New Zealand, eleven hours after it's midnight in England, and 0:05:00.200 --> 0:05:04.159 it's midnight in Samoa. Then the Earth rotates past the 0:05:04.200 --> 0:05:08.360 International dateline. It becomes January second in New England, and 0:05:08.440 --> 0:05:12.280 the cycle repeats. When you imagine how the globe rotates 0:05:12.360 --> 0:05:15.039 with respect to the Sun like this, it's easy to 0:05:15.120 --> 0:05:19.840 keep track of the time zones. Be sure to check 0:05:19.839 --> 0:05:22.960 out our new video podcast, Stuff from the Future. Join 0:05:23.080 --> 0:05:25.599 How Stuff Work staff as we explore the most promising 0:05:25.640 --> 0:05:30.280 and perplexing possibilities of tomorrow. The How Stuff Works I 0:05:30.360 --> 0:05:33.479 Fine app has arrived. Download it today on iTunes.