Hawaii operates on Hawaii Standard Time (HST), which is 10 hours behind Coordinated Universal Time (UTC-10). However, the time difference between Hawaii and the mainland United States varies depending on the time zones of the mainland. During Standard Time in the mainland, Hawaii is 2 hours behind Pacific Standard Time (PST), 3 hours behind Mountain Standard Time (MST), 4 hours behind Central Standard Time (CST), and 5 hours behind Eastern Standard Time (EST). During Daylight Saving Time, which is observed in most parts of the mainland, the time difference remains the same, except for areas that do not observe Daylight Saving Time. It’s always a good idea to double-check the time difference before your trip and adjust your plans accordingly to avoid any confusion.