Standard year-round offset: Riyadh is 6 hours behind Tokyo in both winter (JST UTC+9 → AST UTC+3) and summer (JST UTC+9 → AST UTC+3). When it is 9:00 AM in Tokyo, it is 3:00 AM AST in Riyadh. Best meeting window: 3:00 PM – 5:00 PM JST in Tokyo (9:00 AM – 11:00 AM AST in Riyadh — Golden 9–5 Overlap).
At the standard 6 hours offset (JST to AST), Tokyo and Riyadh share 2 hours/day of simultaneous 9:00 AM – 5:00 PM business hours: 3:00 PM – 5:00 PM JST in Tokyo equals 9:00 AM – 11:00 AM AST in Riyadh.
Both Tokyo (JST) and Riyadh (AST) are simultaneously inside 9:00 AM – 5:00 PM core working hours (2h/day year-round).
Covers 16 hours/day when either Tokyo (JST) or Riyadh (AST) is outside 7:00 AM – 9:00 PM local time.
Because Riyadh is 6 hours behind Tokyo, Riyadh is on the previous calendar day (-1 day) from 12:00 AM until 6:00 AM JST in Tokyo. During that window, Mon–Fri in Tokyo maps to Sun–Thu in Riyadh (and Tue–Sat in Tokyo = Mon–Fri in Riyadh). From 6:00 AM JST to 11:59 PM in Tokyo, both locations are on the same calendar weekday.
Weekend & Workday Alignment: Weekend collision (Tokyo Sat–Sun vs. Riyadh Fri–Sat): Friday is part of the weekend in Riyadh, while Sunday is part of the weekend in Tokyo. In addition, Monday morning in Tokyo before 6:00 AM JST is still Sunday in Riyadh. Standard shared workdays are Monday through Thursday.
Geographically, Tokyo (Japan, 35.68°N, 139.65°E, IATA: HND/NRT) and Riyadh (Saudi Arabia, 24.71°N, 46.68°E, IATA: RUH) are separated by a great-circle distance of 8,689 km (5,399 miles, approximately 10.5h non-stop flight). By longitude, true solar time in Riyadh is 6 hours and 12 minutes behind Tokyo (a 12-minute divergence from the 6 hours standard civil clock offset): Tokyo (35.68°N, 139.65°E) sits 4.65° east of the 135.0°E JST reference meridian, so mean solar noon occurs at 11:41 AM JST year-round, while Riyadh (24.71°N, 46.68°E) sits 1.68° east of the 45.0°E AST reference meridian, so mean solar noon occurs at 11:53 AM AST year-round.
For Tokyo → Riyadh: Arabia Standard Time (AST, UTC+3) is observed year-round across Saudi Arabia, Qatar, Kuwait, Bahrain, and Iraq with no Daylight Saving Time. Note: In North America and the Caribbean, AST denotes Atlantic Standard Time (UTC-4 in winter; ADT UTC-3 in summer).
| Abbreviation Meaning | UTC Offset | IANA Zone | Major Cities & Regions |
|---|---|---|---|
| Arabia Standard Time (Middle East) Primary Here | UTC+3 (year-round, no DST) | Asia/Riyadh | Active on Tokyo → Riyadh: Riyadh, Jeddah (Saudi Arabia), Doha (Qatar), Kuwait City, Baghdad, Manama |
| Atlantic Standard Time (North America & Caribbean) | UTC-4 (ADT UTC-3 in summer; UTC-4 year-round in Puerto Rico) | America/Halifax | Not used for Tokyo → Riyadh: Halifax (Nova Scotia), San Juan (Puerto Rico), Bermuda, Barbados |
For Tokyo → Riyadh: Saudi Arabia officially observes a Sunday–Thursday workweek (Friday–Saturday weekend), though schedules at some multinational private-sector offices vary. When coordinating with Monday–Friday teams in Europe or North America, the standard overlapping workweek is Monday through Thursday (4 days/week).
Computed Friday & Sunday 9–5 Overlap: 0 hours (None). Friday is part of the weekend in Riyadh (Saudi Arabia), and Sunday is part of the weekend in Tokyo (Japan).
Standard shared workdays (Tokyo ↔ Riyadh): Monday through Thursday (4 days/week — 2h/day in winter JST, 2h/day in summer JST).
| Tokyo Time | Riyadh (Standard (JST → AST)) | Day Shift | Call Status |
|---|---|---|---|
| 9:00 AM JST (Morning Start) | 3:00 AM AST | Same day | Overnight / Rest |
| 12:00 PM JST (Midday / Noon) | 6:00 AM AST | Same day | Overnight / Rest |
| 3:00 PM JST (Afternoon) | 9:00 AM AST | Same day | Working Overlap (9–5) |
| 6:00 PM JST (Evening Wrap-up) | 12:00 PM AST | Same day | Shoulder Hours |
| Tokyo (JST) | Riyadh (Standard (JST → AST)) | Day (Riyadh) | Availability (Tokyo ↔ Riyadh) |
|---|---|---|---|
| 12:00 AM JST in Tokyo | 6:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 1:00 AM JST in Tokyo | 7:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 2:00 AM JST in Tokyo | 8:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 3:00 AM JST in Tokyo | 9:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 4:00 AM JST in Tokyo | 10:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 5:00 AM JST in Tokyo | 11:00 PM AST in Riyadh | -1 day | Tokyo–Riyadh Overnight |
| 6:00 AM JST in Tokyo | 12:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 7:00 AM JST in Tokyo | 1:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 8:00 AM JST in Tokyo | 2:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 9:00 AM JST in Tokyo | 3:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 10:00 AM JST in Tokyo | 4:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 11:00 AM JST in Tokyo | 5:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 12:00 PM JST in Tokyo | 6:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Overnight |
| 1:00 PM JST in Tokyo | 7:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 2:00 PM JST in Tokyo | 8:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 3:00 PM JST in Tokyo | 9:00 AM AST in Riyadh | Same day | Tokyo–Riyadh 9–5 |
| 4:00 PM JST in Tokyo | 10:00 AM AST in Riyadh | Same day | Tokyo–Riyadh 9–5 |
| 5:00 PM JST in Tokyo | 11:00 AM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 6:00 PM JST in Tokyo | 12:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 7:00 PM JST in Tokyo | 1:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 8:00 PM JST in Tokyo | 2:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Shoulder |
| 9:00 PM JST in Tokyo | 3:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Late evening / night |
| 10:00 PM JST in Tokyo | 4:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Late evening / night |
| 11:00 PM JST in Tokyo | 5:00 PM AST in Riyadh | Same day | Tokyo–Riyadh Late evening / night |
Neither Tokyo (JST, UTC+9, Asia/Tokyo) nor Riyadh (AST, UTC+3, Asia/Riyadh) observes Daylight Saving Time. Across all 12 months, Riyadh remains 6 hours behind Tokyo.
No Daylight Saving Time observed. Remains on JST (UTC+9) year-round.
No Daylight Saving Time observed. Remains on AST (UTC+3) year-round.
The standard time difference is 6 hours (Riyadh behind Tokyo) in both winter (JST → AST) and summer (JST → AST).
Yes — 4:00 PM JST in Tokyo is 10:00 AM AST (same day) in Riyadh, which is inside standard 9:00 AM – 5:00 PM business hours in both cities.
Aim for 3:00 PM – 5:00 PM JST in Tokyo, which is 9:00 AM – 11:00 AM AST in Riyadh (2h/day of 9–5 overlap). Avoid calling between 9:00 PM – 1:00 PM JST (+1 day) in Tokyo (3:00 PM – 7:00 AM AST (+1 day) in Riyadh), when at least one city is outside 7:00 AM – 9:00 PM.
Neither Tokyo (Asia/Tokyo) nor Riyadh (Asia/Riyadh) observes Daylight Saving Time, so the 6 hours offset never changes.
Because Riyadh officially operates on a Sunday–Thursday workweek (Friday–Saturday weekend) while Tokyo works Monday–Friday (Saturday–Sunday weekend), there is 0 hours of standard business overlap on Fridays and Sundays. Schedule recurring team calls Monday through Thursday (2h/day overlap in winter; 2h/day in summer).