Best hours to reach Guam (+1-671)
Guam runs on Chamorro Standard Time — UTC+10 year-round, no daylight saving. Military, tourism and logistics contacts in Hagåtña are reachable 8 AM–5 PM ChST.
ChST (UTC+10), at a glance.
Guam observes Chamorro Standard Time at UTC+10 all year with no daylight saving. Hagåtña, Tamuning and Dededo all share UTC+10.
Guam against the world's hubs.
Guam is 10 h ahead of London, 2 h ahead of Tokyo and 15 h ahead of New York. Tokyo callers can reach Guam from 10 AM Tokyo time; US West Coast callers must dial in the evening.
Understanding the time difference between the United States and Guam
Time zone differences across other major countries
Why timing matters for calls to Guam.
Guam's defense contractors, port logistics and Japanese tourism contacts start early. The 8–10 AM ChST window catches operations teams before midday, and aligns with Tokyo's early afternoon.
The best windows to reach Guam.
8 AM–11 AM ChST for logistics and defense contacts; 9 AM–12 PM for tourism. From Tokyo, that's 10 AM–1 PM — a comfortable business overlap.
Guam runs at +10:00
The zone is Pacific/Guam. Every window on this page is worked out from that offset rather than a rule of thumb, so the times shown are the ones that actually apply to Guam.
No daylight saving
Guam stays on +10:00 all year. The windows below only move when the caller's own country changes its clocks, not when Guam does.
Shared hours with 2 of 5 markets
Callers in Mumbai, Sydney share part of the working day with Guam. The table above gives the exact intersection for each.
Where the gap is too wide
There is no 9-to-5 overlap with New York, Los Angeles, London. Calling Guam from those cities means someone is working outside normal hours — worth saying so when you book the call.
How to call Guam using the +1-671 code.
Dial +1-671 then the seven-digit local number. Ringflow's NANP routing connects to Hagåtña on Pacific DID infrastructure.
Number anatomy
Dial exit code
Press + on mobile or 00 from most landlines. This opens an international line.
Enter +1-671
Guam's international code. Every call to Guam must start with +1-671.
Area prefix
Add the local area or mobile network code — always drop any leading zero used for domestic calls.
Full number
Dial the remaining subscriber digits. Your number is now correctly formatted for international routing.
Best time to call — every country.
Jump to any country's best-time-to-call guide. Search by name, ISO or dial prefix.
Reach Guam contacts in their window, on the right network.
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When your working day overlaps Guam
Callers in Mumbai and Sydney share part of the working day with Guam. There is no shared working window with New York, Los Angeles and London.
| Calling from | Guam is | Call at (your time) | Which is (their time) |
|---|---|---|---|
| New York | 15h ahead | No shared working hours — you would need to call outside 9am-5pm | |
| Los Angeles | 18h ahead | No shared working hours — you would need to call outside 9am-5pm | |
| London | 10h ahead | No shared working hours — you would need to call outside 9am-5pm | |
| Mumbai | 4h 30m ahead | 9:00 AM – 12:30 PM | 1:30 PM – 5:00 PM |
| Sydney | 1h behind | 10:00 AM – 5:00 PM | 9:00 AM – 4:00 PM |
Windows are the intersection of a 9am-5pm working day in each place, using Guam'sstandard-time offset of +10:00. Guam does not observe daylight saving, so these windows hold all year — though they shift when the caller's own country changes its clocks.
FAQ
Calling Guam, answered.
Time zone, daylight saving and dialling questions for Guam (+1-671).