HDT — Hawaii-Aleutian Daylight Time
See what HDT means, its UTC-9 offset, how it relates to HST during DST, and convert HDT to other time zones.
Meaning and Usage
HDT stands for Hawaii-Aleutian Daylight Time and uses a UTC-9 offset. It is the daylight saving version of the Hawaii-Aleutian time zone.
DST and HST
HDT is observed when daylight saving time is in effect, replacing HST (UTC-10). This page helps you understand the one-hour seasonal shift.
Convert HDT Times
Compare HDT with other time zones using hour-by-hour tables, a visual time grid, and scheduling tools. Export meetings with ICS download or add 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-zone to load the visual comparison grid with HDT already set up. This is useful when you need to line up work across a UTC-9 daylight saving schedule, such as arranging a support handoff, planning travel timing, or comparing availability with teams that do business across Pacific and North American time zones.
Add comparison cities or time zones: Click + Add City and search for the places or time zones you want to compare against HDT. A practical setup is to add markets or offices that also work with AKST, GAMT, or V, since those share the same UTC-9 offset and can help you quickly see whether the same wall-clock hour aligns across multiple operations.
Select the time range on the grid: Click Select to enter selection mode, then drag across the colored 24-hour timeline on the HDT row to highlight the meeting window in purple. You can drag the center of the selection to move it or use the left and right handles to resize it, which is especially helpful when you are trying to compare HDT work hours against another team’s morning shift or evening coverage window.
Export and share the result: Once a range is selected, use the export options for ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. This makes it easy to send a confirmed cross-time-zone slot to remote colleagues, attach it to a project handoff, or drop a ready-made calendar link into email so everyone sees the event in their own local time.
About Hawaii-Aleutian Daylight Time (HDT)
HDT stands for Hawaii-Aleutian Daylight Time. Its exact offset is UTC-9, meaning it is nine hours behind Coordinated Universal Time.
HDT is a daylight saving time abbreviation, not a standard-time abbreviation. Its standard counterpart is HST, so HDT is specifically the daylight-saving version used within the Hawaii-Aleutian time framework when daylight saving time is in effect.
HDT also shares its UTC-9 offset with several other abbreviations: AKST, GAMT, and V. That shared offset is useful when comparing schedules, because a UTC-9 timeline can align numerically across different systems even when the abbreviations and regional naming conventions differ.
HDT and Daylight Saving Time
HDT is the daylight saving form of the Hawaii-Aleutian time designation. When daylight saving time is not in effect, it changes to HST, which is the standard counterpart for the same time system.
If you are scheduling around HDT, the key point is that the abbreviation itself signals that daylight saving time is active. When the seasonal clock change ends, references that were shown as HDT should be updated to HST so meeting invites, operating hours, and travel plans stay consistent.
Because HDT is specifically a DST abbreviation, it is important to confirm whether a given date falls in the daylight-saving part of the year before sending calendar invites or publishing time-sensitive information. That distinction matters for remote teams, customer support coverage, and any workflow where using HDT instead of HST would shift the communicated time standard.
Frequently Asked Questions
What does HDT stand for?
HDT stands for Hawaii-Aleutian Daylight Time. It is the daylight saving version of the Hawaii-Aleutian time designation and uses an exact offset of UTC-9.
Is HDT the same as HST?
No, HDT is not the same as HST. HDT is the daylight saving abbreviation, while HST is its standard-time counterpart, so they refer to different seasonal states within the same broader time system.
Which cities use HDT?
There are no principal cities listed here for HDT. When using the converter, the most reliable approach is to compare the HDT row directly with any cities or time zones you add so you can see how the UTC-9 daylight-saving schedule lines up for your specific use case.
What is the UTC offset for HDT?
The exact UTC offset for HDT is UTC-9. In practical scheduling terms, that means HDT is nine hours behind Coordinated Universal Time and matches the same offset used by AKST, GAMT, and V.
When does HDT change?
HDT changes when daylight saving time is no longer in effect and the designation switches back to HST. Since HDT is itself the daylight-saving abbreviation, it should only be used during the daylight-saving portion of the schedule and replaced with HST outside that period.
Is HDT a daylight saving time abbreviation?
Yes, HDT is explicitly a daylight saving time abbreviation. That is why it is paired with HST as its standard counterpart and why it is important to use the correct abbreviation when creating calendars, timetables, or travel plans.
Are HDT, AKST, GAMT, and V the same thing?
They are not the same abbreviation, but they do share the same UTC-9 offset. That means they can show the same numerical clock difference from UTC even though they belong to different naming systems or regional contexts, which is useful when comparing schedules across multiple time references.