Convert AST to PDT

PDT is 3 hours behind AST. AST is UTC−4 and PDT is UTC−7.

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 5 hours: 12:00 PM–5:00 PM AST (9:00 AM–2:00 PM PDT). Schedule meetings inside that window.

AST to PDT conversion table

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.

About PDT

Pacific Daylight Time (PDT) is UTC−7. It is used in Los Angeles, San Francisco and Seattle from March to November.

Pacific Daylight Time is UTC−7, the summer clock for Los Angeles, San Francisco, Seattle and Vancouver. It is the zone most product launches and software release times are quoted in, and it is worth converting rather than eyeballing: PDT is eight hours behind British Summer Time, not seven, because both sides have moved.

Does this gap change with the seasons?

This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on PDT switches to PST (UTC−8) from November to March. So the 3-hour figure on this page is correct for the part of the year when both places are actually on these abbreviations, and changes by an hour outside it.

AST does not shift, so the whole change comes from one side. A recurring meeting fixed in AST will appear to move by an hour for everyone on the other side, twice a year, without anyone changing anything.

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 AST conversions

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

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