Chamorro Time Zone
The Chamorro Time Zone, formerly the Guam Time Zone, is a United States time zone which observes standard time ten hours ahead of Coordinated Universal Time (UTC+10:00). The clock time in this zone is based on the mean solar time of the 150th meridian east of the Greenwich Observatory.
The zone includes the U.S. territories of Guam and the Northern Mariana Islands, where the Chamorro people are the original inhabitants. Since Daylight Saving Time (DST) is not observed anywhere in this zone, the time is always known as Chamorro Standard Time (ChST).
Chamorro Standard Time shares the same time as Australian Eastern Standard Time.
The Mariana Islands were not part of any time zone legislated by the U.S. Congress until the Chamorro time zone was established by Public Law 106-564 on December 23, 2000. Prior to 2000, Guam's standard time was based on territorial Public Law 5-25 (1959) which designated the time Guam Standard Time. The law (Guam Code Annotated, Title 1, Section 1010) was established long before the Northern Mariana Islands came under U.S. sovereignty in 1986, and still remains in the book today despite federal overlap.