Tamuning, Guam · UTC+10 ☆

Tamuning is the main commercial center of Guam, a US territory in the western Pacific, containing the island’s major hotels, shopping centers, and business district. It runs on Chamorro Standard Time (UTC+10) all year, with no daylight saving.

Guam at UTC+10 is one of the first US-administered territories to experience each calendar day. When it is Monday morning in Tamuning, much of the US mainland is still in Sunday. The island is often cited as the place “where America’s day begins,” a marketing phrase that captures the unusual temporal position of this US territory in the western Pacific.

At 13 degrees north, Guam has minimal seasonal daylight variation: about 13 hours in June, about 11.5 hours in December. The fixed offset needs no adjustment.

Chamorro identity and colonial time

Guam was a Spanish colony for over 200 years before the US took possession in 1898. The island’s Chamorro people, the indigenous population, have navigated multiple colonial temporal regimes. The calendar name Chamorro Standard Time was formally adopted in recent years, acknowledging the indigenous cultural identity alongside the administrative timezone.

Tamuning-Tumon-Harmon Village, listed separately in some databases, effectively covers the same commercial and tourist zone.

Tamuning-Tumon-Harmon Village is adjacent, sharing the same clock.

9am in Tamuning is 11pm in London the previous day in winter, 10pm during British Summer Time.

Sources

• IANA Time Zone Database
• Guam Visitors Bureau