North Korean officials announced Friday that the country is creating its own time zone, moving back 30 minutes on Aug. 15. The establishment of "Pyongyang time" is a political move intended to erase the legacy of Japanese colonial rule a century ago. Before that, the entire Korean peninsula was 8½ hours ahead of GMT, the time that North Korea will now revert to.
Here is a look at ways in which countries have changed their time zones for political reasons:
—HOW IT ALL BEGAN: Time zones were first proposed in the mid-19th century as global travel and communication gathered pace. But it wasn't until the early 20th century that time zones were standardized with reference to Greenwich Mean Time (GMT), after the meridian that runs through an observatory in the London borough of Greenwich. Most countries now use hourly offsets from GMT, but some large countries use multiple time zones while some small ones use fractions of an hour that more closely reflect the passage of the sun in their territory.
—GREAT LEAP BACKWARD: China, a vast nation stretching almost 5,000 kilometers (3,100 miles) from one end to the other, used to have five time zones. After taking power in 1949, the Communist Party abolished all except "Beijing time" (GMT +8) to simplify governance and to bring cohesion to the diverse nation. The decision has created problems for those living in the country's west, particularly Tibet and Xinjiang, whose residents rise two hours earlier than they naturally would to be in synch with the east. Some residents set their clocks back by two hours to reflect actual conditions, an unofficial practice sometimes interpreted as disloyalty to Beijing.
—15 MINUTES OF FAME: In 1956 Nepal moved to GMT +5:45 to mark the time the sun passes over a famous mountain, becoming one of only three places to have the quarter-hour offset. Proposals to adopt the same time zone as neighboring India (GMT +5:30), which surrounds Nepal on three sides, have gone nowhere.
—TEA TIME: Stretching 1,800 miles from east to west, India has long struggled to reconcile itself to clocks. India was divided into two time zones for most of its history as a British colony, then chose a unified time zone upon independence. But some in the country's far east still go their own way. In Assam state, home to much of India's tea industry, many plantations work on what they call chaibagaan, or "tea garden time": Clocks are set one hour ahead so field hands have more sunlight.
—WHAT TIME IS IT? For many years Sri Lanka operated on two different time zones simultaneously. The central government set the country's clocks back by 30 minutes in 1996, seeking more daylight hours during a power crisis. But Tamil Tiger rebels, who controlled wide swathes of northern Sri Lanka and were always looking for ways to prove their political independence, refused to follow. The government's time now stands; the Tigers were crushed in 2009.
—SPRING FORWARD: Last year the Ukrainian province of Crimea jumped one time zone eastward to reflect its annexation by Russia. On March 30, 2014, clocks in Crimea were moved forward two hours to synchronize with Moscow. Crimea also gave up daylight savings time since Russia doesn't observe it, so it's now two hours ahead of Ukraine in the winter and one hour in the summer.
—NAZI TIME: Until the 1940s, Spain was on the same time as Britain and Portugal, which are on roughly the same latitude. But when Nazi-occupied France switched to German time, Spain's Franco dictatorship followed suit and the country never went back. A petition to switch back to British time has gathered some support in recent years and in 2013 a parliamentary commission said a switch could have profound effects on eating, sleeping and working habits in Spain, famed for long lunches, siestas and late shifts at work. So far, nothing has come of the proposal.
—BACK AND FORTH: Venezuela was 4½ hours behind GMT until 1965, when it shifted to GMT -4 to conform to international standards. Former President Hugo Chavez, who railed against U.S. domination in the Americas, moved back to the half-hour offset in 2007 in a move that critics said was motivated mainly by politics. Chavez said he didn't want kids waking up in the dark to go to school, but the move put a strain on an economy already facing power shortages because lights went on earlier in the evening.
—IS IT SATURDAY ALREADY? On Dec. 29, 2011, the Pacific island nation of Samoa — not to be confused with American Samoa — became only the second country to jump across the international dateline. The shift means that it is now usually the same day in Samoa as in its biggest trading partners, New Zealand and Australia.
Christopher Bodeen in Beijing, Binaj Gurubacharya in Kathmandu, Tim Sullivan in New Delhi, Ciaran Giles in Madrid and Joshua Goodman in Bogota, Colombia, contributed to this report.