The Chamorro Time Zone, formerly the Guam Time Zone, is a United States time zone which observes

standard time Standard time is the synchronization of clocks within a geographical region to a single time standard, rather than a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the r ...

ten hours ahead of

Coordinated Universal Time Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communicat ...

( UTC+10:00). The clock time in this zone is based on the

mean solar time Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Traditionally, there are three types of time reckoning based ...

of the

150th meridian east Fifteen or 15 may refer to: *15 (number) *one of the years 15 BC, AD 15, 1915, 2015 Music *Fifteen (band), a punk rock band Albums * ''15'' (Buckcherry album), 2005 * ''15'' (Ani Lorak album), 2007 * ''15'' (Phatfish album), 2008 * ...

of the

Greenwich Observatory The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in G ...

. The zone includes the

U.S. territories Territories of the United States are sub-national administrative divisions and dependent territories overseen by the federal government of the United States. The American territories differ from the U.S. states and Indian reservations in th ...

Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...

and the

Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...

, where the

Chamorro people The Chamorro people (; also Chamoru) are the Indigenous peoples of Oceania, Indigenous people of the Mariana Islands, politically divided between the Territories of the United States, United States territory of Guam and the encompassing Norther ...

are the original inhabitants. Since

Daylight Saving Time Daylight saving time (DST), also referred to as daylight savings time, daylight time (Daylight saving time in the United States, United States and Daylight saving time in Canada, Canada), or summer time (British Summer Time, United Kingdom, ...

(DST) is not observed anywhere in this zone, the time is always known as Chamorro Standard Time (ChST). The zone is two hours behind Wake Island Time Zone and 15 hours ahead of North American

Eastern Time Zone The Eastern Time Zone (ET) is a time zone encompassing part or all of 23 U.S. states, states in the eastern part of the United States, parts of eastern Canada, and the state of Quintana Roo in Mexico. * Eastern Standard Time (EST) is five ...

. As of March 19, 2024 it is the easternmost (farthest ahead) time zone shown on the U.S. government's time.gov webpage. Although Wake, Howland and Baker Islands are U.S. territories in more easterly time zones (that are not shown), they are uninhabited. Chamorro Standard Time shares the same time as

Australian Eastern Standard Time Australia uses three main time zones: Australian Eastern Standard Time (AEST; UTC+10:00), Australian Central Standard Time (ACST; UTC+09:30) and Australian Western Standard Time (AWST; UTC+08:00). Time is regulated by the individual states a ...

. The State of

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

also does not observe DST, so the Commonwealth of the Northern Mariana Islands (CNMI), Guam and Queensland are on the same time year round.

Populated areas and major cities

Hagåtña, Guam Hagåtña, formerly Agana or Agaña, is a coastal village and the capital of the United States territory of Guam. From the 18th through mid-20th century, it was Guam's population center, but today, it is the second smallest of the island's 19 ...

Saipan, Northern Mariana Islands Saipan () is the largest island and capital of the Northern Mariana Islands, an unincorporated territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Census Bureau, the population of Saipa ...

History

Until the end of 1844,

and

Mariana Islands The Mariana Islands ( ; ), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st pa ...

belonged to

Captaincy General of the Philippines The Captaincy General of the Philippines was an administrative district of the Spanish Empire in Southeast Asia governed by a governor-general as a dependency of the Viceroyalty of New Spain based in Mexico City until Mexican independence when i ...

, which followed the date of the western hemisphere on their island, placing them on the eastern side of the

International Date Line The International Date Line (IDL) is the line extending between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and de ...

(IDL). At the end of Monday, December 30, 1844, both Guam and Mariana Islands continued directly to Wednesday, January 1, 1845, effectively removing Tuesday, December 31, 1844 from the calendar to follow the eastern hemisphere on the west side of the IDL and realign themselves from American to Asian dates. Before time zones were introduced, every place used local observation of the sun to set its clocks, which meant that every location used a different local mean time based on its longitude. For example, Hagåtña, the capital of Guam at the time, at longitude 144°45′E, had a local time equivalent to GMT-14:21 under the date of the western hemisphere and GMT+09:39 under the eastern hemisphere. In 1901, "Guam Standard Time" was established within the United States as GMT+10:00. The U.S. Congress formally created Chamorro Standard Time by federal Public Law 106-564 on December 23, 2000. Previously, ''Guam'' Standard Time existed per territorial Public Law 5-25 (1959).Guam Code Annotated, Title 1, Section 1010
textPDF
. This statute is still on the territorial law books, although it is preempted by the federal law. The Northern Mariana Islands, as part of the

Trust Territory of the Pacific Islands The Trust Territory of the Pacific Islands (TTPI) was a United Nations trust territory in Micronesia administered by the United States from 1947 to 1994. The Imperial Japanese South Seas Mandate had been seized by the U.S. during the Pacifi ...

, were not part of any American time zone prior to becoming a U.S. Commonwealth on January 1, 1978. Being directly north of Guam, however, they observed the same time.

References

{{reflist

Sources

Current time around the world
Time zones Time zones in the United States

Populated areas and major cities

History

See also

References

Sources