• Menu
  • Menu

Time difference calculation

HOME » Time difference calculation

UTC, Coordinated Universal Time

UTC (Coordinated Universal Time) is the "Universal Coordinated Time" that is the basis for determining the standard time around the world.
Japan Standard Time is "UTC + 9" because it is 9 hours ahead of (UTC).

In the past, "Global Standard Time" was determined by the average solar time at the Greenwich Observatory on the outskirts of London, England, and was called Greenwich Mean Time (GMT).
At present, however, the world standard time uses "UTC" which is modified and defined based on the atomic clock.

There are two time systems: universal time and atomic time.

Universal time is the universal time represented by the mean solar angle at 12 o'clock relative to the prime meridian passing through Greenwich, England, based on astronomical observations, and is called Universal Time (UT).
And GMT (Greenwich mean time) is the local mean time of Greenwich (0 degrees longitude) in the UK (noon when the mean sun is south of the south).

Atomic time is a time system based on the frequency of cesium atoms, and high-precision atomic clocks that do not deviate by about one millionth of a second per year are being developed.
And as a result of the development of the atomic clock, it turned out that the rotation speed of the earth fluctuates, and various problems have arisen when continuing to use the universal time in which the unit of seconds constantly fluctuates.
For this purpose, the most stable atomic clock was adopted as the reference clock, and the international atomic time was started with the universal time of 00:00:00 on January 1, 1958 as the starting point. Atomic time of each country is averaged by international comparison, and the atomic time of each country is compared with this international atomic time later, and there is an international agreement that the difference is within one millionth of a second. Yes).
However, if this international atomic time is used as it is, the deviation from the universal time gradually increases due to fluctuations in the rotation speed of the earth, causing inconvenience in real life.
Therefore, UTC (Coordinated universal time) was adjusted in leap seconds so that the error between international atomic time and universal time did not exceed 0.9 seconds.
In other words, the time standard is adjusted so that the display of the sun's operation and time is not so disturbed while maintaining the accuracy of atomic time, and the time used in daily life is this UTC.


Time zone list

* This mark indicates the country where daylight savings time is implemented. The implementation period is one hour earlier.

Coordinated Universal TimeCountry / Region
UTC-12Baker Island, Howland Island
UTC-11American Samoa, Niue
UTC-10Western Aleutian Islands, Cook Islands, Hawaii, French Polynesia
UTC-9:30French Polynesia (Marquise Islands)
UTC-9* Alaska
UTC-8* America Pacific Time, * Canada Pacific Time (Vancouver, Whitehorse, Dawson City), Clipperton Island, Pitcairn Islands, * Mexico Pacific Time (Tijuana)
UTC-7* American Mountain Time, * Canadian Mountain Time (Edmonton, Calgary, Yellowknife, Inuvik), Canadian Mountain Time (, Dawson Creek, Fort Nelson, Creston), * Mexican Mountain Time (Chihuahua, Mazatlan), Mexican Mountain Time (Hermosillo)
UTC-6* Central United States time, El Salvador, * Central Canada time (Winnipeg, Rankin Inlet, Rainy River, Resolute,), Central Canada time (Regina), Guatemala, Costa Rica, Nicaragua, Belize, Honduras, * Central Mexico time (Mexico City, Guadalajara) (Merida, Monterrey)
UTC-5* Eastern U.S.A., Ecuador, * Eastern Canada (Toronto, Ottawa, Thunder Bay, Montreal), E.C. , * Bahamas, Brazil Acre Time (Rio Blanco, Eirnepe), Peru
UTC-4* Canadian Atlantic Time (Happy Valley Goose Bay, Moncton, Halifax, Grace Bay), Canadian Atlantic Time (Bran Sablon), Curacao, Guadeloupe, Grenada, Saint Barthelemy, Saint Martin, Sint Maarten, Saint Christopher Nevis, St. Vincent, St. Lucia, * Chile, Dominica, Dominican Republic, Trinidad and Tobago, * Bermuda, * Paraguay, Barbados, Puerto Rico, * Brazil Amazon Time (Cuiaba, Campo Grande), Brazil Amazon Time (Bore Vista, Manaus, Porto Velho), Venezuela, Bonaire, Sint Eustatius, Bolivia, Martinique, Montserrat
UTC-3:30* Canada Newfoundland Time (St. Johns)
UTC-3Argentina, * Greenland, Uruguay, * Saint Pierre Island, * Mikron Island, Suriname, Falkland Islands, * Brazil Time (Brazilia, Belo Horizonte, Rio de Janeiro, Sao Paulo, Curitiba, Porto Alegre), Brazil Time (Bahia, Maceio, Recife, Natal, Fortaleza, Araguaina, Santarem), French Guiana
UTC-2South Georgia South Sandwich Islands, Brazil Fernando de Noronha Time (Fernando de Noronha)
UTC-1Azores, Cape Verde
UTC+0* United Kingdom, * Ireland, * Iceland, Ghana, * Guernsey, Gambia, Guinea, Guinea-Bissau, Ivory Coast, Sierra Leone, * Jersey, Senegal, St. Helena, Togo, * West Sahara, * Faroe Islands, Bouvet, Burkina Faso, * Portugal, Mali, * Isle of Man, Mauritania, * Morocco, Liberia
UTC+1Algeria, * Albania, Angola, * Andorra * Italy, * Austria, * Netherlands, Gabon, Cameroon, * Croatia, Congo, Sao Tome and Principe, * San Marino, * Gibraltar, * Switzerland, * Svalbard, * Sweden, * Spain , * Slovakia, Equatorial Guinea, * Czech, Chad, Central Africa, Tunisia, * Denmark, * Germany, Nigeria, Niger, * Norway, * Vatican, * Hungary, * France, Benin, * Belgium, * Bosnia and Herzegovina, * Poland , * Macedonia, * Malta, * Monaco, * Montenegro, * Liechtenstein, * Luxembourg
UTC+2* Israel, * Ukraine, Egypt, * Estonia, * Aland Islands, * Cyprus, * Greece, Zambia, * Syria, Zimbabwe, Sudan, Swaziland, Namibia, * Palestine, * Finland, * Bulgaria, Burundi, Botswana, Malawi, South Africa , Mozambique, * Moldova, * Jordan, * Latvia, * Lithuania, Libya, Rwanda, * Romania, Lesotho, * Lebanon, Russia Kaliningrad time (Kaliningrad)
UTC+3Yemen, Iraq, Uganda, Ethiopia, Eritrea, Qatar, Kuwait, Kenya, Comoros, Saudi Arabia, Djibouti, Somalia, Tanzania, Turkey, Bahrain, Belarus, Madagascar, Mayotte, South Sudan, Russia Moscow Time (Moscow)
UTC+4Azerbaijan, United Arab Emirates, Armenia, Oman, Georgia, Seychelles, Mauritius, Reunion, Russia Samara time (Samara)
UTC+5Uzbekistan, Tajikistan, Turkmenistan, Heard and Macdonald Islands, Pakistan, Maldives, Russia and Yekaterinburg time (Ekaterinburg)
UTC+5:30India, Sri Lanka
UTC+6Kazakhstan, Kyrgyzstan, Bangladesh, Bhutan, RussiaOmsk Time (Omsk)
UTC+6:30Cocos Islands, Myanmar
UTC+7Indonesia, Dawson Creek, Cambodia, Christmas Island, Thailand, Vietnam, Laos, Russia Krasnoyarsk time (Krasnoyarsk)
UTC+8Western Australia Time (Perth), Singapore, Taiwan, China, Philippines, Brunei, Hong Kong, Macau, Malaysia, Mongolia, Russia Irkutsk Time (Irkutsk)
UTC+8:45Australia Midwest Time (Eucla)
UTC+9Japan, South Korea, North Korea, Palau, East Timor, RussiaYakutsk time (Yakutsk)
UTC+9:30Australian Central Time (Darwin)
UTC+10Australian Eastern Time (Brisbane, Cairns, Hamilton Island), Northern Mariana Islands, Guam, Papua New Guinea, Federated States of Micronesia, RussiaVladivostok Time (Vladivostok)
UTC+10:30Central Australia Time (Adelaide, Lord Howe Island)
UTC+11* Australia Eastern Time (Sydney, Canberra, Melbourne), Solomon Islands, New Caledonia, Norfolk Island, Vanuatu, Russia Magadan Time (Magadan)
UTC+12Wallis and Futuna, Kiribati, Tuvalu, Nauru, * New Zealand, * Fiji, Marshall Islands, Russia Kamchatka Time (Kamchatka)
UTC+12:45New Zealand (Chatham Island)
UTC+13* Samoa, Tokelau Islands, Tonga
UTC+14Kiribati (Line Islands)


Example of calculating the time difference from Japan:
Example 1) In the case of Los Angeles, USA, the time zone of California Pacific Time (UTC-8) is California.
UTC-8 stands for eight hours behind standard time.
Japan is 9 hours ahead of standard time because UTC + 9.
To find the time difference between Los Angeles and Japan, subtract the lagging Los Angeles figure from the advanced Japan number.
9-(-8) = 17, right? The time difference is 17 hours.
During summer time, subtract one hour from here.
So 16 hours.

Example 2) For Paris, France, the time zone is UTC + 1.
This is one hour ahead of standard time.
As in Los Angeles, you can find the time difference by subtracting UTC + 1 in Paris from UTC + 9 in Japan.
9-1 = 8 8 hours time difference.
During summer time, subtract one hour from here.
So it will be 7 hours.