Technical Specifications & Standards
Official chronometric properties, ISO standards, and international database registry identifiers for Chamorro Standard Time:
Daylight Saving Time (DST) Transitions
⬆️ Spring Forward (Clocks Advance)
None (Equatorial proximity)
⬇️ Fall Back (Clocks Return)
None
Observing Jurisdictions & Subdivisions
2 Sovereign NationsSovereign nations, administrative subdivisions, and regional territories officially operating under ChST:
Regional Subdivisions & Territory Details
Financial Markets & Trading Hours
Connects US federal defense logistics and western Pacific tourism with Tokyo, Manila, and Honolulu.
Local Hours: 09:00 - 16:00 ChST
UTC Window: 23:00 - 06:00 UTC
Major Cities in ChST
Primary metropolitan centers and financial hubs observing this time zone:
Adoption History & Astronomical Facts
Year Established: 2000
Previously called Guam Standard Time, Public Law 106-564 officially renamed the zone to Chamorro Standard Time in 2000 in recognition of the indigenous Chamorro people of the Mariana Islands.
Because Guam observes ChST (UTC+10), it is the first American territory to greet each new calendar day, inspiring the official territorial slogan: 'Where America's Day Begins.'
Frequently Asked Questions about ChST
What does ChST stand for?
ChST stands for Chamorro Standard Time, which is 10 hours ahead of UTC (UTC+10).
What territories observe Chamorro Standard Time?
The US territories of Guam and the Northern Mariana Islands observe ChST.
Does Guam observe Daylight Saving Time?
No. Guam stays on UTC+10 all year.