HDT time now (Hawaii-Aleutian Daylight Time)

What HDT means

HDT stands for Hawaii-Aleutian Daylight Time, UTC−9. It is used in the western Aleutian Islands of Alaska.

It is a summer time: the daylight saving form of HST (UTC−10), one hour ahead. In Adak it applies from March to October/November: from the second Sunday of March at 2:00 AM to the first Sunday of November at 2:00 AM.

Where and when HDT is used

1 zone uses it for part of the year only, switching back to standard time in the other months. Computed from tzdata under the current rules.

How long HDT has been used

In the tzdata record, Adak has used HDT since 1984.

HDT in the past

Zones whose tzdata history shows HDT before 2025 but that no longer use it:

• Pacific/Honolulu (Honolulu): 1933

HDT converted to other zones

Every column is a fixed offset, so this table is valid on any date. Remember that the regions behind some columns switch to summer time (EST to EDT, CET to CEST, GMT to BST); the clock in those cities is then an hour later than the column.

Related zones and conversions

• HST time
• America/Adak time zone
• UTC−9 time
• Time zones of the world
• Daylight saving time
• Time zone converter