HDT — Hawaii-Aleutian Daylight Time
See what HDT means, when this UTC-9 daylight saving time is used, and convert it to other time zones with live comparisons.
Meaning and usage areas
HDT stands for Hawaii-Aleutian Daylight Time and uses a UTC-9 offset. It is used during daylight saving time in parts of the Hawaii-Aleutian time zone, primarily in the Aleutian Islands region.
DST and HST relationship
HDT is the daylight saving counterpart to HST, which runs at UTC-10 during standard time. This page shows when clocks shift between HST and HDT and updates automatically for DST changes.
Convert to other zones
Compare HDT with other time zones using the visual time grid and hour-by-hour tables. Export meeting times with ICS download or send them to Google Calendar and Gmail.
How to Convert HDT to Other Time Zones
Open the HDT converter page: Go to
https://www.xconvert.com/time-converter/hdt-time-zoneto open the visual comparison grid with HDT pre-loaded as the reference row. This layout is useful when you need to line up Hawaii-Aleutian Daylight Time with another schedule, such as planning a remote meeting, a travel handoff, or a support shift that touches UTC-9 hours.Add comparison cities or time zones: Click + Add City and search for the locations or time zones you want to compare against HDT. If you work across Pacific and North American schedules, add the cities or zones your team actually uses so you can see how HDT lines up against customer support windows, airline operations, or partner availability.
Select the time range on the grid: Click Select, then drag across the colored hourly slots on the HDT row to highlight the meeting or work window you want to compare. You can drag the purple selection by its center to move it, or adjust the left and right handles to fine-tune the exact span for a call, shift overlap, or booking window.
Export and share the selected time: After selecting a range, use the export options for ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. This is practical when you need to send a confirmed time block to a distributed team so each person sees the event in their own local calendar without manually converting from HDT.
About Hawaii-Aleutian Daylight Time (HDT)
HDT stands for Hawaii-Aleutian Daylight Time. Its exact offset is UTC-9, which means the time zone is nine hours behind Coordinated Universal Time.
HDT is a daylight saving time abbreviation, not a year-round standard time designation. Its standard counterpart is HST, so HDT is used as the daylight version within the Hawaii-Aleutian time framework.
Other abbreviations that share the same UTC-9 offset include AKST, GAMT, and V. That shared offset can be useful when comparing systems, logs, or schedules that display different abbreviations but align to the same UTC difference.
HDT and Daylight Saving Time
HDT is specifically a daylight saving time abbreviation, which means it represents the daylight-saving portion of the Hawaii-Aleutian time system rather than the standard-time portion. When daylight saving time is not in effect, the corresponding standard abbreviation is HST.
If you are scheduling across seasons, the key practical point is that HDT changes to HST when daylight saving time ends, and HST changes to HDT when daylight saving time begins. Exact transition dates for the current year are not included here, so the most reliable use of this page is understanding that HDT is the DST form and HST is the standard counterpart.
Frequently Asked Questions
What does HDT stand for?
HDT stands for Hawaii-Aleutian Daylight Time. It is the daylight saving time abbreviation used within the Hawaii-Aleutian time system rather than the standard-time label.
Is HDT the same as HST?
No, HDT is not the same as HST. HDT is the daylight saving version, while HST is the standard counterpart used when daylight saving time is not in effect.
What is the UTC offset for HDT?
HDT uses an exact offset of UTC-9. In practical terms, that means HDT is nine hours behind Coordinated Universal Time.
Which cities use HDT?
Specific principal cities are not identified here. The important point for conversion is that HDT refers to Hawaii-Aleutian Daylight Time, so when you see HDT on schedules, calendars, or system timestamps, you should interpret it as UTC-9 daylight time within that time framework.
Which countries use HDT?
A country list is not included here. For scheduling and conversion purposes, the most important detail is the abbreviation itself: HDT means Hawaii-Aleutian Daylight Time at UTC-9.
When does HDT change?
HDT changes when daylight saving time starts or ends within the Hawaii-Aleutian time system. When daylight saving time ends, HDT switches to HST; when daylight saving time begins again, HST switches back to HDT.
Is HDT a daylight saving time zone?
Yes, HDT is a daylight saving time abbreviation. That is why it has a standard counterpart, HST, which is used outside the daylight saving period.
Are there other abbreviations with the same offset as HDT?
Yes. Other abbreviations that share the same UTC-9 offset are AKST, GAMT, and V. This matters when comparing timestamps from different systems, because the abbreviations may differ even when the UTC offset is identical.