Convert HST to AST

AST is 6 hours ahead of HST. HST is UTC−10 and AST is UTC−4.

Which AST is this?

AST names more than one zone. This page reads it as Atlantic Standard Time at UTC−4, which is the reading most converters take. There is one other: Arabia Standard Time at UTC+3, used in Saudi Arabia, Iraq, Kuwait, Bahrain, Qatar and Yemen.

The letters on a meeting invitation do not say which one is meant. If yours is not Atlantic Standard Time, the answer above is wrong, and not by a little:

The large converter sites disagree about this as well: search for a AST conversion and some of the results answer for one reading and some for another, none of them saying which they chose. Where it matters, ask which country the sender is in rather than which letters they typed.

Best time to schedule a meeting

Standard 9–5 working hours overlap for 2 hours: 9:00 AM–11:00 AM HST (3:00 PM–5:00 PM AST). Schedule meetings inside that window.

HST to AST conversion table

About HST

Hawaii Standard Time (HST) is UTC−10. It is used in Hawaii, which does not observe daylight saving at all.

Hawaii–Aleutian Standard Time is UTC−10 and Hawaii does not observe daylight saving. That makes it the North American zone whose relationship to everywhere else changes twice a year without it doing anything: Hawaii is two hours behind Los Angeles in winter and three in summer. It is also far enough west that the working day barely overlaps with the US east coast at all.

About AST

Atlantic Standard Time (AST) is UTC−4. It is used in Halifax, Puerto Rico and the eastern Caribbean in winter.

Atlantic Standard Time is UTC−4, one hour ahead of Eastern. It covers Canada's Atlantic provinces, Puerto Rico and much of the eastern Caribbean, and it is the reason a call from Halifax to Toronto is an hour out from what either party expects. The abbreviation is also used for Arabia Standard Time at UTC+3, seven hours away in the other direction, which is a genuinely dangerous collision in scheduling.

Does this gap change with the seasons?

Neither HST nor AST shifts with the seasons, so this 6-hour difference holds all year. That is unusual enough to be worth relying on: most cross-continental gaps move twice a year.

This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.

Frequently asked questions

Other HST conversions

• HST to UTC
• HST to GMT
• HST to EST
• HST to EDT
• HST to CST
• HST to CDT
• HST to MST
• HST to MDT
• HST to PST
• HST to PDT
• HST to AKST
• HST to BRT
• HST to BST
• HST to CET
• HST to CEST
• HST to EET

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