Hawaii does not change clocks
Hawaii stays at UTC−10 throughout the year and does not observe daylight saving. Mainland clocks change seasonally, so the time difference is not the same all year.
When the mainland is on daylight time, Hawaii is three hours behind Pacific time and six behind Eastern time. During mainland standard time, the differences are two and five hours. The live clocks on this site use timezone rules rather than a fixed mainland offset.
Make opening hours unambiguous
Write “Hawaii time” beside booking and office hours. A mainland customer arranging a trip should not have to infer which timezone the business uses.
For scheduled callbacks, repeat the date and both relevant time zones. If your booking system handles conversions, test what a customer in another timezone actually sees.
Plan the call that comes too early
A voicemail greeting can state the business name, Hawaii-time hours, and a practical next step. An email or booking form is useful only if your business actually monitors it.
A new number does not include 24-hour answering. Ask the provider about routing and voicemail, and make sure published expectations match the service you operate.