Why does time zone change

Daylight Saving Starts in Morocco on April 3, Samoa Starts Daylight Saving on September Daylight Saving Starts in Mexico on April 3, Daylight Saving Starts in Cuba on March 20, Europe Starts Daylight Saving on March 27, Countries Consider Canceling Daylight Saving. Russia Abolishes Winter Time. Daylight Saving Ends in Europe on October 31, Australia Starts Daylight Saving on October 3, Brazil Starts Daylight Saving on October 17, Russia Reduces Number of Time Zones.

Daylight Saving Time Returns to Egypt in No Daylight Saving in Pakistan in No Daylight Saving Time in Bangladesh in Time Zone Changes in Antarctica in Time Zone Change is Possible in Venezuela.

No Daylight Saving for South Korea in Guatemala Considers Daylight Saving Revival. Time Zone Changes in Antarctica. Ireland Considers Central European Time. Talks of Time Change in Nepal. Mexico's Clocks Turn Back on October 25, New Time Zone for Kemerovo in Russia.

Pakistan ends DST on November 1, Samoa's Daylight Saving Starts in September Pakistan starts Daylight Saving Time April 15, Tunisia Abandons Daylight Saving Time in Samoa Starts Daylight Saving Time in Jersey Rejects Central European Time. South Australia Extends Daylight Saving in — Pakistan Extends Daylight Saving Hours in Mauritius turns the clock forward in October Morocco revives daylight saving schedule in Pakistan turns to daylight saving to address power crisis.

Europe Embarks on Daylight Saving Schedule Syria Observes Daylight Saving Time Cuba starts Daylight Saving Time on March 16, Iraq Dumps Daylight Saving Time in Indiana Unites for Daylight Saving Time.

Venezuela: Clocks to be set back 30 minutes on December 9, So, can bars serve alcohol for that additional hour? Some states claim that bars actually stop serving liquor at a. Other states solve the problem by saying that liquor can be served until "two hours after midnight. Most people were at home and this was the time when the fewest trains were running. It is late enough to minimally affect bars and restaurants, and it prevents the day from switching to yesterday, which would be confusing.

It is early enough that the entire continental U. For the U. The Navajo Nation participates in the Daylight Saving Time policy, even in Arizona, due to its large size and location in three states.

Many fire departments encourage people to change the batteries in their smoke detectors when they change their clocks because Daylight Saving Time provides a convenient reminder. But DST has far wider ramifications, for energy use, farming, even mood.

Some argue that DST does not really save energy , as less household usage in the evenings in summer might be offset by greater morning usage.

Health impacts are widely touted: people can get more exposure to sunlight through the summer DST months, boosting their vitamin D levels. But critics argue that disruption to circadian rhythms sleep patterns can negatively impact on human health. Studies have found that the risk of having a heart attack increases in the first three weekdays after switching to DST in the spring.

However they also found that the extra hour of sleep after the clocks went back in autumn decreased the risk of heart attacks in the first few weekdays after switching. DST is thought to have an impact on the economy but again it is a mixed picture. While the retail and tourism industries do benefit from the extra hour of summer evening daylight, that may well be offset by some of the health effects mentioned above.

The farming industry has traditionally disliked DST for its impact on everything from milking cows to reaping harvests. But an NFU spokesman painted a more nuanced picture. The aviation sector is little affected. Plane schedules have to work around the issue of countries changing clocks at different times.

Peak driving times are between 8am and 10am in the morning between 3pm and 7pm in the afternoon. When the clocks move back in autumn, it means that the majority of these peak hours in the afternoon are in darkness. The dateline, and standard time zones in convenient hourly chunks, dates from 's International Meridian Conference. Nor did the meridian conference specify the exact course of the dateline.

It zigs and zags as it crosses land or passes through island groups. It kinks east to encompass Siberia within the same date as the rest of Russia, and west to bring Hawaii into line with mainland US. Over the years, many countries have ignored this international standard and set their own time as a way to assert national identity, to make political connections, or to keep one time zone within their borders.

Some opt for local time based on the position of the sun, says Rebekah Higgitt, curator of the history of science and technology at the Royal Observatory in Greenwich.

In , Venezuela's president Hugo Chavez shifted the entire country back 30 minutes. Swapping sides of the dateline is not a first for Samoa. It, and neighbouring American Samoa, lay west of the dateline until , when a US businessman convinced both to switch to the east for trading purposes.