JST to AST
-13hJST
JSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
JST and AST on the World Map
The map below highlights the JST (Japan Standard Time) and AST (Atlantic Standard Time) timezone regions across the globe.
JST – Japan Standard Time
UTC+09:00Japan Standard Time (JST) is the time zone for Japan, 9 hours ahead of UTC.
- •Japan does not observe daylight saving time.
- •Tokyo is the most populous metropolitan area in the world.
- •The Tokyo Stock Exchange operates from 9:00 AM to 3:00 PM JST.
- •JST is 14 hours ahead of EST and 9 hours ahead of GMT.
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •Puerto Rico uses AST year-round and does not observe DST.
- •AST is 1 hour ahead of EST.
- •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
JST to AST Time Difference – Complete Guide
JST runs on Japan Standard Time (JST) at UTC+09:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts JST 13 hours behind AST — a difference of -13h at the current offsets.
In practice, when it is 9:00 AM in JST it is 8:00 PM in AST on the previous day. Midnight in JST is 11:00 AM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
JST to AST time conversion table
| JST (JST) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 11:00 AM | previous day |
| 6:00 AM | 5:00 PM | previous day |
| 7:00 AM | 6:00 PM | previous day |
| 8:00 AM | 7:00 PM | previous day |
| 9:00 AM | 8:00 PM | previous day |
| 12:00 PM | 11:00 PM | previous day |
| 3:00 PM | 2:00 AM | same day |
| 5:00 PM | 4:00 AM | same day |
| 6:00 PM | 5:00 AM | same day |
| 9:00 PM | 8:00 AM | same day |
Why people convert JST to AST time
- Scheduling a call from JST to AST: a 10:00 AM start in JST lands at 9:00 PM in AST the previous day, so you can confirm the slot without doing the arithmetic yourself.
- Handling a -13h gap: JST and AST have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in AST is 8:00 PM in JST.
- Watching a live event or market open: JST viewers need 8:00 PM in AST to catch a 9:00 AM start there, and 1:00 PM if the event is anchored to JST.
- Always state the zone abbreviation, not just the hour. "3:00 PM JST" is unambiguous; "3 PM" across a -13h gap is not.
- With a -13h gap there is no shared 9-to-5 window, so alternate the early start: one week JST takes the early slot, the next week AST does.
About JST (Japan Standard Time)
Japan Standard Time (JST) is the standard time zone for all of Japan. Japan does not observe daylight saving time. JST is 9 hours ahead of UTC and 14 hours ahead of EST. The Tokyo Stock Exchange, the world's third largest by market capitalization, operates on JST. South Korea uses the same offset (KST) but it is a distinct time zone.
About AST (Atlantic Standard Time)
Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.
Best time to call between JST and AST
With a -13h offset there is no overlap inside a normal 9 AM – 5 PM day. AST opens at 9:00 AM AST, which is 8:00 PM in JST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
JST and AST have no shared working hours because of the -13h gap. Teams need to alternate early starts or rely on asynchronous handovers.
JST is 13 hours behind AST (JST UTC+09:00 → AST UTC-04:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
JST
Does not observe DST
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between JST and AST?
JST (JST, UTC+09:00) is 13 hours behind AST (AST, UTC-04:00). The gap is currently -13h.
How do I convert JST time to AST time?
Add -13h to JST local time. For example, 9:00 AM in JST is 8:00 PM in AST (previous day).
What time is it in AST right now?
AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -13h offset from JST.
What is the best time to call AST from JST?
There is no shared working-hours window because of the -13h gap. The closest option is 1:00 PM in JST, which is 12:00 AM in AST.
Which is behind, JST or AST?
JST is 13 hours behind AST. When it is 12:00 PM in JST it is 11:00 PM in AST.
Does daylight saving time affect the JST–AST difference?
Neither zone observes daylight saving time, so the -13h offset between JST and AST is fixed all year.
Which other cities share JST's time zone?
JST also covers Tokyo, Osaka, Yokohama, Nagoya, Sapporo, Kyoto, Kobe, Fukuoka and 1 more.
Which countries use JST, JST's zone?
JST is used in Japan.
Is there a day difference between JST and AST?
Sometimes. The -13h gap is large enough that 8:00 PM or later in JST already falls on the in AST.
What is the time difference between JST and AST?
AST is -13h from JST.
What timezone is JST in?
JST operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use JST (Japan Standard Time)?
JST is used in Japan.
Does JST observe daylight saving time?
No, JST does not observe daylight saving time and remains at UTC+09:00 year-round.
What are some interesting facts about JST?
Japan does not observe daylight saving time. Tokyo is the most populous metropolitan area in the world.
Which cities are in the AST timezone?
Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
What is the UTC offset for AST?
Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.
What should I know about the AST timezone?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
When is it midnight in JST, what time is it in AST?
When it is 12:00 AM (midnight) in JST (JST), it is -13h later in AST (AST).
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See every conversion from JST →·See every conversion from AST →