Hawaii is in the Hawaii-Aleutian Time Zone, or HAST. It shares this time zone with Alaska and the Aleutian Islands during parts of the year.

Hawaii-Aleutian Time is 10 hours behind Coordinated Standard Time. This places it five hours behind Eastern Standard Time, the time zone observed in Washington, D.C. This can sometimes lead to conflicts, such as when, in 2015, the federal health insurance website shut down for maintenance in the middle of the day, Hawaiian-time.

Hawaii shares this time zone with other U.S. states and territories only during the winter and spring. While Alaska observes Daylight Saving Time and switches to Hawaii-Aleutian Daylight Time during the summer and HAST during the winter, Hawaii uses HAST all year-round.