AST to JST Converter
Understanding AST and JST Time Zones
Atlantic Standard Time (AST)
Atlantic Standard Time is observed in undefined and uses the offset UTC-4. Major cities in this time zone include Halifax, San Juan. This time zone serves a significant global region with important economic and cultural hubs.
Japan Standard Time (JST)
Japan Standard Time operates at UTC+9, covering undefined. Key cities include Tokyo, Osaka, Yokohama. The 13-hour forward offset from AST means that when professionals in Halifax start their workday at 9:00 AM, it is already 10:00 PM in Tokyo.
AST is also commonly referred to as Atlantic Time, Puerto Rico time. JST is also known as Japan time, Tokyo time, Japanese time. So if you are searching for Atlantic Time to Japan time, this is the same conversion as AST to JST.
Complete AST to JST Conversion Table
The table below shows every two-hour increment converted from Atlantic Standard Time to Japan Standard Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| AST (Atlantic Standard Time) | JST (Japan Standard Time) |
|---|---|
| 12:00 AM (00:00) | 1:00 PM (13:00) |
| 2:00 AM (02:00) | 3:00 PM (15:00) |
| 4:00 AM (04:00) | 5:00 PM (17:00) |
| 6:00 AM (06:00) | 7:00 PM (19:00) |
| 8:00 AM (08:00) | 9:00 PM (21:00) |
| 10:00 AM (10:00) | 11:00 PM (23:00) |
| 12:00 PM (12:00) | 1:00 AM (01:00) (next day) |
| 2:00 PM (14:00) | 3:00 AM (03:00) (next day) |
| 4:00 PM (16:00) | 5:00 AM (05:00) (next day) |
| 6:00 PM (18:00) | 7:00 AM (07:00) (next day) |
| 8:00 PM (20:00) | 9:00 AM (09:00) (next day) |
| 10:00 PM (22:00) | 11:00 AM (11:00) (next day) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between AST and JST
Remote teams spanning Halifax and Tokyo often adopt asynchronous practices to bridge the 13-hour gap. Tools like Slack, Loom, and Notion reduce the need for real-time overlap while keeping projects moving forward.
The large 13-hour gap between AST and JST means that finding overlapping working hours requires compromise from at least one side. Consider adopting asynchronous workflows — recorded video updates, shared documents, and time-zone-aware project management tools — to supplement the limited real-time overlap.
Travel Between Halifax and Tokyo
When arriving in Tokyo from Halifax, immediately set all devices to local time. Exposure to natural daylight at the destination helps reset your circadian rhythm. Eastbound travelers should seek morning light.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 13-hour shift between AST and JST, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.
For the AST to JST conversion specifically: AST (UTC-4) and JST (UTC+9) neither observes DST, so the 13-hour offset remains constant throughout the year. This makes scheduling reliable and predictable.
Related Time Zone Conversions
References & Resources
Frequently Asked Questions
AST (Atlantic Standard Time) is 13 hours behind JST (Japan Standard Time). AST is UTC-4 and JST is UTC+9.
When it is 12:00 PM (noon) in AST, it is 1:00 AM (next day) in JST.
The best overlap for business hours is approximately 10:00 PM to 6:00 AM JST, which corresponds to 9:00 AM to 5:00 PM in AST. Given the large gap, consider alternating between early and late meeting times.
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.