Current Time in ChST (Chamorro Standard Time)
About ChST
Used in Guam and the Northern Mariana Islands, which are US territories in the western Pacific Ocean. This time zone does not observe daylight saving time and is ten hours ahead of Coordinated Universal Time.
UTC Offset: +10:00
Current time shown is based on the representative IANA zone: Pacific/Guam
Chamorro Standard Time (ChST): A Complete Guide
Chamorro Standard Time (ChST) is the time zone observed year-round in the U.S. territories of Guam and the Northern Mariana Islands. With a fixed UTC offset of +10:00, ChST does not observe daylight saving time, making it a consistent reference for travelers, businesses, and military operations in the western Pacific.
What Is Chamorro Standard Time?
Chamorro Standard Time, abbreviated ChST, is named after the indigenous Chamorro people of the Mariana Islands. It is also known as Guam Standard Time in some contexts. The zone is defined by its constant UTC offset of +10:00 hours, meaning it is 10 hours ahead of Coordinated Universal Time. Unlike many time zones in the United States and elsewhere, ChST does not shift to daylight saving time, so the offset remains the same throughout the year.
Regions and Cities
ChST is used exclusively in the following U.S. territories:
- Guam โ an island territory in Micronesia, with the capital Hagรฅtรฑa and the largest city Dededo.
- Northern Mariana Islands โ a commonwealth including the islands of Saipan, Tinian, and Rota. The capital is Capitol Hill on Saipan.
The IANA time zone database lists two identifiers under ChST: Pacific/Guam and Pacific/Saipan. Both follow the same offset and rules, so they are functionally identical.
Comparison with Neighboring Time Zones
ChST sits in a region with several other time zones. Here is how it compares to its neighbors:
- Japan Standard Time (JST, UTC+9) โ ChST is 1 hour ahead of Japan. When it is noon in Tokyo, it is 1:00 PM in Guam.
- Australian Eastern Standard Time (AEST, UTC+10) โ ChST shares the same offset as AEST during standard time. However, when Australia observes daylight saving (AEDT, UTC+11), ChST is 1 hour behind Sydney.
- Palau Time (PWT, UTC+9) โ ChST is 1 hour ahead of Palau.
- Chuuk Time (CHUT, UTC+10) โ ChST is identical to Chuuk Time, used in parts of Micronesia.
- Wake Island Time (WAKT, UTC+12) โ ChST is 2 hours behind Wake Island.
Because ChST does not observe DST, its offset relative to zones that do change seasonally. For example, during the U.S. mainland's daylight saving time (e.g., EDT, UTC-4), ChST is 14 hours ahead; during standard time (EST, UTC-5), it is 15 hours ahead.
Practical Business Hours Guidance
For those scheduling calls or coordinating with Guam or Saipan, here are typical working hours (Monday to Friday, 8:00 AM to 5:00 PM ChST) converted to major time zones:
- New York (EST/EDT): 5:00 PM to 2:00 AM (EST) or 6:00 PM to 3:00 AM (EDT) the previous day. Best overlap: early morning EST (8-9 AM) corresponds to late evening ChST (9-10 PM).
- Los Angeles (PST/PDT): 2:00 PM to 11:00 PM (PST) or 3:00 PM to 12:00 AM (PDT) previous day. Overlap: late afternoon PST (4-5 PM) is early morning ChST (8-9 AM next day).
- London (GMT/BST): 10:00 PM to 7:00 AM (GMT) or 11:00 PM to 8:00 AM (BST). Overlap: late evening BST (9-10 PM) is early morning ChST (6-7 AM next day).
- Tokyo (JST): 7:00 AM to 4:00 PM JST. Full overlap with ChST working hours (8 AM-5 PM ChST = 7 AM-4 PM JST).
- Sydney (AEST/AEDT): 8:00 AM to 5:00 PM AEST (same as ChST). During AEDT, Sydney is 1 hour ahead, so 8 AM ChST = 9 AM Sydney.
For best overlap with U.S. East Coast, schedule calls around 7:00-9:00 AM EST (which is 9:00-11:00 PM ChST) or early morning ChST (8:00-10:00 AM) which is late afternoon/evening EST (6:00-8:00 PM).
Key Facts
- ChST is used by about 180,000 people across Guam and the Northern Mariana Islands.
- The zone is critical for U.S. military operations, as Guam hosts Andersen Air Force Base and Naval Base Guam.
- No daylight saving time has been observed in these territories since they came under U.S. control.
- The name "Chamorro" honors the indigenous people, and the abbreviation ChST is officially recognized by the U.S. Department of Transportation.
Frequently Asked Questions
Does Chamorro Standard Time observe daylight saving time?
No, ChST does not observe daylight saving time. The offset remains UTC+10:00 year-round.
What is the time difference between ChST and U.S. Eastern Time?
During Eastern Standard Time (EST, UTC-5), ChST is 15 hours ahead. During Eastern Daylight Time (EDT, UTC-4), ChST is 14 hours ahead.
Are Guam and Saipan in the same time zone?
Why is it called Chamorro Standard Time?
The name comes from the Chamorro people, the indigenous inhabitants of the Mariana Islands. It reflects the cultural heritage of the region.
What is the IANA time zone identifier for ChST?
The IANA identifiers are Pacific/Guam and Pacific/Saipan. Both represent the same offset and rules.
How does ChST compare to Australian time zones?
ChST matches Australian Eastern Standard Time (AEST, UTC+10) but is 1 hour behind Australian Eastern Daylight Time (AEDT, UTC+11) when DST is in effect.