The Chamorro Time Zone
, formerly the Guam Time Zone
, observes standard time
by adding ten hours to Coordinated Universal Time
). The clock time in this zone is based on the mean solar time
of the 150th degree meridian
east of the Greenwich Observatory
The zone includes the U.S. territories of Guam and the Northern Mariana Islands. Daylight Saving Time is not observed anywhere in the zone; hence the time in this zone is always known as Chamorro Standard Time (ChST).
The zone is two hours behind Wake Island Time Zone, 15 hours ahead of North American Eastern Time Zone, and 18 hours ahead of Pacific Time Zone.
Chamorro Standard Time is practically the same time as Australian Eastern Standard Time.
Populated Areas and Major Cities
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.