AST to JST: AST is 12 hours behind JST

Atlantic Time is 12 hours behind Japan Standard Time right now. It is 7:09 am ADT in Atlantic and 7:09 pm JST in Japan.

Convert a specific time from AST to JST

Pick any time and date to convert it both ways. The conversion runs in your browser against the real zone rules, so a date inside a daylight saving period gets that period's offset rather than today's.

What is the time difference between AST and JST?

Japan Standard Time is 12 hours ahead of Atlantic Time. To go from AST to JST you add 12 hours. That gap is not fixed. Across 2026 the distance between these two zones takes 2 different values, from 12 hours to 13 hours, because Atlantic moves its clocks and Japan does not. This page recomputes it rather than assuming.

AST to JST conversion table

Every hour of Friday, September 25, 2026 in Atlantic, with the matching reading in Japan. 12 of the 24 hours land on a different calendar date in Japan, which is the part people get wrong when they schedule across this pair.

What are the best hours to schedule a call between AST and JST?

No hour of the standard 9:00 am to 5:00 pm working day falls inside working hours on both sides. Atlantic and Japan are 12 hours apart, which is too far for an overlap, so somebody has to take a call outside their own working day. The least painful options are below, ranked by how close both sides sit to the middle of the afternoon.

Does daylight saving change AST to JST?

Atlantic Time is currently on ADT and changes next on Sunday, November 1, 2026, when the clock falls back from 1:59 am to 1:00 am and the offset moves from UTC-3 to UTC-4.

Japan Standard Time does not move its clocks at all, so its UTC+9 offset holds every day of the year.

Because the two sides do not move together, the answer to this conversion changes during the year. For part of the year the gap is 12 hours and for the rest it is 13 hours. The table above is built for today, not for an average day.

Is AST ahead of or behind JST?

AST is behind JST by 12 hours: when it is 12:00 pm in Atlantic, it is 12:00 am the next day in Japan. One wrinkle worth knowing: AST and ADT are two names for the same zone, not two zones. Atlantic Time reads AST in winter and ADT in summer. When somebody types "ast to jst" they nearly always mean the zone rather than the literal winter offset, so this page resolves AST to America/Halifax and JST to Asia/Tokyo and applies whichever offset is genuinely in force on the day.

Atlantic Time covers Halifax, Moncton and the Canadian Maritimes. Japan Standard Time covers Tokyo, Osaka and the whole of Japan. The identifiers behind them are America/Halifax and Asia/Tokyo, which is what any calendar or scheduling system should be storing rather than a fixed number of hours.

Questions

What is AST in JST?

AST is 12 hours behind JST. 9:00 am AST is 9:00 pm JST.

How many hours ahead is JST of AST?

JST is 12 hours ahead of AST. That varies across the year, between 12 hours and 13 hours.

What time is it in Japan right now?

7:09 pm JST on Friday, September 25, 2026.

When can Atlantic and Japan meet during working hours?

There is no shared working hour. The closest fit is 7:00 am AST, which is 7:00 pm JST.

Does this account for daylight saving?

Yes. Every reading is computed from the IANA database for the actual date, so ADT and JST are the abbreviations genuinely in force today rather than a fixed assumption.

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