Chicago is 9 hours behind Riyadh in winter (AST UTC+3 → CST UTC-6) and 8 hours behind in summer (AST UTC+3 → CDT UTC-5). A 9:00 AM start in Riyadh is 12:00 AM CST in winter and 1:00 AM CDT in summer in Chicago. Best meeting window — Winter (AST): 6:00 PM – 9:00 PM AST (9:00 AM – 12:00 PM CST); Summer (AST): 4:30 PM – 7:30 PM AST (8:30 AM – 11:30 AM CDT).
With a 9 hours gap in Winter (AST) (AST → CST) and a 8 hours gap in Summer (AST) (AST → CDT), Riyadh and Chicago have 0 hours of simultaneous 9:00 AM – 5:00 PM business hours in either season. Meetings use morning and early-evening shoulder windows within 7:00 AM – 9:00 PM local time.
Optimal Riyadh–Chicago shoulder bridge for Winter (AST) (9 hours gap) and Summer (AST) (8 hours gap), ending at or before 9:00 PM local time.
Covers every hour where Riyadh or Chicago is outside 7:00 AM – 9:00 PM local time (19h/day in Winter (AST); 18h/day in Summer (AST)).
| Riyadh Time | Chicago (Winter (AST → CST)) | Day Shift | Chicago (Summer (AST → CDT)) | Call Status |
|---|---|---|---|---|
| 9:00 AM AST (Morning Start) | 12:00 AM CST | Same day | 1:00 AM CDT | Overnight / Rest |
| 12:00 PM AST (Midday / Noon) | 3:00 AM CST | Same day | 4:00 AM CDT | Overnight / Rest |
| 3:00 PM AST (Afternoon) | 6:00 AM CST | Same day | 7:00 AM CDT | Overnight / Rest |
| 6:00 PM AST (Evening Wrap-up) | 9:00 AM CST | Same day | 10:00 AM CDT | Shoulder Hours |
| Riyadh (AST) | Chicago (Winter (AST → CST)) | Day (Chicago) | Chicago (Summer (AST → CDT)) | Availability (Riyadh ↔ Chicago) |
|---|---|---|---|---|
| 12:00 AM AST in Riyadh | 3:00 PM CST in Chicago | -1 day | 4:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 1:00 AM AST in Riyadh | 4:00 PM CST in Chicago | -1 day | 5:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 2:00 AM AST in Riyadh | 5:00 PM CST in Chicago | -1 day | 6:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 3:00 AM AST in Riyadh | 6:00 PM CST in Chicago | -1 day | 7:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 4:00 AM AST in Riyadh | 7:00 PM CST in Chicago | -1 day | 8:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 5:00 AM AST in Riyadh | 8:00 PM CST in Chicago | -1 day | 9:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 6:00 AM AST in Riyadh | 9:00 PM CST in Chicago | -1 day | 10:00 PM CDT (-1 day) | Riyadh–Chicago Overnight |
| 7:00 AM AST in Riyadh | 10:00 PM CST in Chicago | -1 day | 11:00 PM CDT (-1 day) | Riyadh–Chicago Late evening / night |
| 8:00 AM AST in Riyadh | 11:00 PM CST in Chicago | -1 day | 12:00 AM CDT | Riyadh–Chicago Late evening / night |
| 9:00 AM AST in Riyadh | 12:00 AM CST in Chicago | Same day | 1:00 AM CDT | Riyadh–Chicago Overnight |
| 10:00 AM AST in Riyadh | 1:00 AM CST in Chicago | Same day | 2:00 AM CDT | Riyadh–Chicago Overnight |
| 11:00 AM AST in Riyadh | 2:00 AM CST in Chicago | Same day | 3:00 AM CDT | Riyadh–Chicago Overnight |
| 12:00 PM AST in Riyadh | 3:00 AM CST in Chicago | Same day | 4:00 AM CDT | Riyadh–Chicago Overnight |
| 1:00 PM AST in Riyadh | 4:00 AM CST in Chicago | Same day | 5:00 AM CDT | Riyadh–Chicago Overnight |
| 2:00 PM AST in Riyadh | 5:00 AM CST in Chicago | Same day | 6:00 AM CDT | Riyadh–Chicago Overnight |
| 3:00 PM AST in Riyadh | 6:00 AM CST in Chicago | Same day | 7:00 AM CDT | Riyadh–Chicago Overnight |
| 4:00 PM AST in Riyadh | 7:00 AM CST in Chicago | Same day | 8:00 AM CDT | Riyadh–Chicago Shoulder |
| 5:00 PM AST in Riyadh | 8:00 AM CST in Chicago | Same day | 9:00 AM CDT | Riyadh–Chicago Shoulder |
| 6:00 PM AST in Riyadh | 9:00 AM CST in Chicago | Same day | 10:00 AM CDT | Riyadh–Chicago Shoulder |
| 7:00 PM AST in Riyadh | 10:00 AM CST in Chicago | Same day | 11:00 AM CDT | Riyadh–Chicago Shoulder |
| 8:00 PM AST in Riyadh | 11:00 AM CST in Chicago | Same day | 12:00 PM CDT | Riyadh–Chicago Shoulder |
| 9:00 PM AST in Riyadh | 12:00 PM CST in Chicago | Same day | 1:00 PM CDT | Riyadh–Chicago Late evening / night |
| 10:00 PM AST in Riyadh | 1:00 PM CST in Chicago | Same day | 2:00 PM CDT | Riyadh–Chicago Late evening / night |
| 11:00 PM AST in Riyadh | 2:00 PM CST in Chicago | Same day | 3:00 PM CDT | Riyadh–Chicago Late evening / night |
Between Riyadh (Saudi Arabia, Asia/Riyadh) and Chicago (United States, America/Chicago), the seasonal offset shifts by 1 hour. In winter standard time (AST vs. CST), Chicago (UTC-6) is 9 hours behind Riyadh (UTC+3). In summer (AST vs. CDT), Chicago (UTC-5) is 8 hours behind Riyadh (UTC+3).
No Daylight Saving Time observed. Remains on AST (UTC+3) year-round.
| Date Window | Duration | Active Zones | Time Difference | Regime |
|---|---|---|---|---|
| Since Nov 1, 2026 | 133 days | AST (UTC+3) → CST (UTC-6) | 9 hours | Standard Alignment (Active Now) |
| Mar 14, 2027 – Nov 2, 2027 | 233 days | AST (UTC+3) → CDT (UTC-5) | 8 hours | Standard Alignment |
Because Chicago is 9 hours behind Riyadh in winter and 8 hours behind in summer, Chicago remains on the previous calendar day (-1 day) from 12:00 AM until 9:00 AM AST in winter (8:00 AM AST in summer) in Riyadh. During those hours, Sun–Thu in Riyadh maps to Sat–Wed in Chicago (and Tue–Sat in Riyadh maps to Mon–Fri in Chicago). After 9:00 AM AST (8:00 AM AST in summer), both locations share the same weekday.
Weekend & Workday Alignment: Weekend collision (Riyadh Fri–Sat vs. Chicago Sat–Sun): Friday is part of the weekend in Riyadh, while Sunday is part of the weekend in Chicago. In addition, Monday morning in Riyadh before 9:00 AM AST is still Sunday in Chicago. Standard shared workdays are Monday through Thursday.
Geographically, Riyadh (Saudi Arabia, 24.71°N, 46.68°E, IATA: RUH) and Chicago (United States, 41.88°N, 87.63°W, IATA: ORD/MDW) are separated by a great-circle distance of 11,247 km (6,989 miles, approximately 13.5h non-stop flight). By longitude, true solar time in Chicago is 8 hours and 57 minutes behind Riyadh (a 3-minute divergence from the 9 hours standard civil clock offset): 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, while Chicago (41.88°N, 87.63°W) sits 2.37° east of the 90.0°W CST reference meridian, so mean solar noon occurs at 11:51 AM CST in winter and 12:51 PM CDT in summer.
For Riyadh → Chicago: 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 Riyadh → Chicago: 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 Riyadh → Chicago: Halifax (Nova Scotia), San Juan (Puerto Rico), Bermuda, Barbados |
For Riyadh → Chicago: Literal North American CST (Central Standard Time) is UTC-6, observed from early November to mid-March (and year-round in Mexico City). During summer Daylight Saving Time, Chicago and Texas observe CDT (Central Daylight Time, UTC-5).
| Abbreviation Meaning | UTC Offset | IANA Zone | Major Cities & Regions |
|---|---|---|---|
| Central Standard Time (North America) Primary Here | UTC-6 (CDT UTC-5 in summer) | America/Chicago | Active on Riyadh → Chicago: Chicago, Dallas, Houston, Austin, Winnipeg, Mexico City |
| China Standard Time | UTC+8 (year-round) | Asia/Shanghai | Not used for Riyadh → Chicago: Beijing, Shanghai, Shenzhen, Taipei |
| Cuba Standard Time | UTC-5 (CDT UTC-4 in summer) | America/Havana | Not used for Riyadh → Chicago: Havana, Cuba |
For Riyadh → Chicago: 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 Chicago (United States).
Standard shared workdays (Riyadh ↔ Chicago): Monday through Thursday (4 days/week — 0h/day in winter AST, 0h/day in summer AST).
In winter (standard time), Chicago (CST, UTC-6) is 9 hours behind Riyadh (AST, UTC+3). In summer (daylight saving time), Chicago (CDT, UTC-5) is 8 hours behind Riyadh (AST, UTC+3).
4:00 PM in Riyadh corresponds to 7:00 AM CST (same day) in winter and 8:00 AM CDT (same day) in summer in Chicago, placing it inside waking hours (7:00 AM – 9:00 PM) in both cities.
In winter (AST), the best window is 6:00 PM – 9:00 PM AST in Riyadh (9:00 AM – 12:00 PM CST in Chicago). In summer (AST), use 4:30 PM – 7:30 PM AST in Riyadh (8:30 AM – 11:30 AM CDT in Chicago). Avoid hours outside 7:00 AM – 9:00 PM local time (9:00 PM – 4:00 PM AST (+1 day) in winter; 9:00 PM – 3:00 PM AST (+1 day) in summer).
Riyadh: No DST (AST year-round). Chicago: Sun, Mar 14, 2027 (CST → CDT, new gap: 8 hours (CDT UTC-5 vs AST UTC+3)).
Because Riyadh officially operates on a Sunday–Thursday workweek (Friday–Saturday weekend) while Chicago 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 (0h/day overlap in winter; 0h/day in summer).