Why do we have timezones?
914543
at different times on the earth the sun is at different positions in the sky. When it's noon somewhere, it's midnight on the direct opposite side of the earth. If a particular time was called 12 noon to everyone it would seem silly to the people where it was midnight.
24749
Probably because the server is located on the West coast...this is normally why there is a difference. The service itself doesn't really have anything that would be time specific enough to call for them to allow users to set their own time zone...
1078661
I prefer daylight saving time.
672574
In 1878, Canadian Sir Sanford Fleming proposed the system of worldwide time zones that we use today. He recommended that the world be divided into twenty-four time zones, each spaced 15 degrees of longitude apart. Since the earth rotates once every 24 hours and there are 360 degrees of longitude, each hour the earth rotates one-twenty-fourth of a circle or 15 degrees of longitude. Sir Fleming's time zones were heralded as a brilliant solution to a chaotic problem worldwide.\n\nUnited States railroad companies began utilizing Fleming's standard time zones on November 18, 1883. In 1884 an International Prime Meridian Conference was held in Washington D.C. to standardize time and select the Prime Meridian. The conference selected the longitude of Greenwich, England as zero degrees longitude and established the 24 time zones based on the Prime Meridian. Although the time zones had been established, not all countries switched immediately. Though most U.S. states began to adhere to the Pacific, Mountain, Central, and Eastern time zones by 1895, Congress didn't make the use of these time zones mandatory until the Standard Time Act of 1918.\n\nToday, many countries operate on variations of the time zones proposed by Sir Fleming. All of China (which should span five time zones) uses a single time zone - eight hours ahead of Coordinated Universal Time (known by the abbreviation UTC - based on the time zone running through Greenwich at 0 degrees longitude). Australia uses three time zones - its central time zone is a half-hour ahead of its designated time zone. Several countries in the Middle East and South Asia also utilize half-hour time zones.\n\nSince time zones are based on segments of longitude and lines of longitude narrow at the poles, scientists working at the North and South Poles simply use UTC time. Otherwise, Antarctica would be divided into 24 very thin time zones!\n\nThe time zones of the United States are standardized by Congress and although the lines were drawn to avoid populated areas, sometimes they've been moved to avoid complication. There are nine time zones in the U.S. and its territories, they include Eastern, Central, Mountain, Pacific, Alaska, Hawaii-Aleutian, Samoa, Wake Island, and Guam.\n\nWith the growth of the Internet and global communication and commerce, some have advocated a new worldwide time system.
467810
I think that when you first sign up to Yahoo! it asks you what time zone you are in. If you got it wrong or if you are at the edge of that time zone that would explain the time difference. Mine does it too. Its a real pain.
740211
Japan is GMT +9 and Arizona is GMT -7. Add on 7 hours to get GMT and then add on the extra 9 hours and so you get 4 AM the following day.\n\nHope this helps,\n\nSupreme One
1076030
Originally, the local time at the Royal Observatory, Greenwich, England was chosen as standard at the 1884 International Meridian Conference, leading to the widespread use of Greenwich Mean Time (GMT) in order to set local clocks. This location was chosen because by 1884 two-thirds of all charts and maps already used it as their Prime Meridian. In 1929 the term Universal Time (UT) was introduced to refer to GMT with the day starting at midnight. Until the 1950s broadcast time signals were based on UT, and hence on the rotation of the Earth.
1092478
There is no use apart from being in time with the rest of the world.\n\nIn some parts it is not wise to put the clocks forward/backwards as this will change what time it is at the hottest in a day.\n\nChina is one of the few counties that does do this.
196749
no, it's because of the rotation of the earth.  Clocks in the southern hemisphere go around the other direction, like your toilet ;-).\n\nIt's because the shadow on a sun dial in England goes around that direction.
480279
because it relies to the events which can't be measured metrically anyway. Weeks follow the approximate lunar circle, there's 365 days in a year etc.\n\nalso, imagine we would divide a day into 100 hours. 1 hour would last only 14 minutes, which would be way too few and confusing. \nIf we divided a day into 10 hours, an hour would last 2 hours and 64 minutes. this would probably be too long, and we wouldn't have enough hours to properly determine a time of day...\n\nAn hour was determined as 1/4 of the time when the shadow of a pole travels a 60 degree angle or something... i THINK. I might be wrong on this, high school phisics is a LONG time ago. \nAnyway, it was old Sumerians or Babilonians who determined it like that and ever since it wasn't changed. We're too used to these units now, we can't just change them without causing a massive MESS :D
250437
The main purpose of Daylight Saving Time (called "Summer Time" in many places in the world) is to make better use of daylight. We change our clocks during the summer months to move an hour of daylight from the morning to the evening. Countries have different change dates. Glide your cursor over the map to see how changing the clocks affects different latitudes.\n\nIf you live near the equator, day and night are nearly the same length (12 hours). But elsewhere on Earth, there is much more daylight in the summer than in the winter. The closer you live to the North or South Pole, the longer the period of daylight in the Summer. Thus, Daylight Saving Time (Summer Time) is usually not helpful in the tropics, and countries near the equator generally do not change their clocks. \n\nA poll done by the U.S. Department of Transportation indicated that Americans liked Daylight Saving Time because "there is more light in the evenings / can do more in the evenings." A 1976 survey of 2.7 million citizens in New South Wales, Australia found 68% liked daylight saving. \n\nDaylight Saving Time also saves energy. Studies done by the U.S. Department of Transportation show that Daylight Saving Time trims the entire country's electricity usage by a small but significant amount, about one percent each day, because less electricity is used for lighting and appliances. Similarly, in New Zealand, power companies have found that power usage decreases 3.5 percent when daylight saving starts. In the first week, peak evening consumption commonly drops around five percent.\n\nEnergy use and the demand for electricity for lighting homes is directly related to the times when people go to bed at night and rise in the morning. In the average home, 25 percent of electricity is used for lighting and small appliances, such as TVs, VCRs, and stereos. A good percentage of energy consumed by lighting and appliances occurs in the evening when families are home. By moving the clock ahead one hour, the amount of electricity consumed each day decreases.\n\n\nIn the Summer, people who rise before the sun rises use more energy in the morning than if DST was not in effect. However, although 70 percent of Americans rise before 7:00 a.m., this waste of energy from having less sunlight in the morning is more than offset by the savings of energy that results from more sunlight in the evening.\n\nIn the Winter, the afternoon Daylight Saving Time advantage is offset for many people and businesses by the morning's need for more lighting. In Spring and Fall, the advantage is generally less than one hour. So, Daylight Saving Time saves energy for lighting in all seasons of the year, but it saves least during the four darkest months of Winter (November, December, January, and February), when the afternoon advantage is offset by the need for lighting because of late sunrise.\n\nIn addition, less electricity is used because people are home fewer hours during the "longer" days of Spring and Summer. Most people plan outdoor activities in the extra daylight hours. When people are not at home, they don't turn on the appliances and lights.\n\nThere is a public health benefit to Daylight Saving Time, as it decreases traffic accidents. Several studies in the U.S. and Great Britain have found that the DST daylight shift reduces net traffic accidents and fatalities by close to one percent. An increase in accidents in the dark mornings is more than offset by the evening decrease in accidents.
162199
"Greenwich, England has been the home of Greenwich Mean Time (GMT) since 1884.  GMT is sometimes called Greenwich Meridian Time because it is measured from the Greenwich Meridian Line at the Royal Observatory  in Greenwich.  It is the place from where all time zones are measured. \nThe Greenwich Meridian (Prime Meridian or Longitude Zero degrees) marks the starting point of every time zone in the World.  GMT is Greenwich Mean (or Meridian) Time is the mean (average) time that the earth takes to rotate from noon-to-noon.  \n\nGMT is World Time and the basis of every world time zone which sets the time of day and is at the centre of the time zone map.  GMT sets current time or official time around the globe.  Most time changes are measured by GMT.  Although GMT has been replaced by atomic time (UTC) it is still widely regarded as the correct time for every international time zone."
715356
Daylight Savings Time is practiced is not limited to the U.S. alone.  Many states around the world employ DST.  It's primary justification is energy-savings; By adjust the clock to take advantage of the longer daylight of summer, less artifical light is required.\n\nDaylight Savings was first put into practice by Germany during WorldWar I, and was quickly adopted by the U.S. and much of Europe.
280177
Which time zone do you live in?
610875
Time zones are for the most part uneven and follow geographic lines like shore lines and rivers and political lines such as boundrys between countrys. In a perfect world time zones would be just over 1000 miles at the equator and gradually get smaller as they move toward the poles.
69368
5:00 P.M. As you move east your time gets later, and as you move west your time gets earlier.  There is a time zone for roughly every 15 degrees of longitude.\nThus it would be 4:00 P.M. Central, and 2:00 P.M. Pacific.
67128
Find here:\nhttp://www.worldtimezone.com/