Tonga uses Tonga Standard Time (TOT), which is UTC+13 hours during Standard Time and UTC+13 hours during Daylight Saving Time (TOT), as they typically do not observe DST.

Tonga does not currently observe Daylight Saving Time, so the country remains on Tonga Standard Time (UTC+13) throughout the year. However, there have been periods in the past when Tonga did observe DST.

The time difference between Tonga and the United States varies depending on the U.S. time zone. For example, Tonga is 19 hours ahead of Pacific Standard Time (PST) and 18 hours ahead of Eastern Standard Time (EST) during Standard Time.

Tonga shares its time zone (TOT, UTC+13) with a few other Pacific islands, such as parts of Kiribati and Samoa when Samoa observes Daylight Saving Time.