Time Difference: Chicago and London
London is 6 hours ahead of Chicago for most of the year and 5 hours ahead for a few weeks. 9:00 AM in Chicago is 3:00 PM in London normally and 2:00 PM in the 5-hour weeks.
Daylight saving note: London is 6 hours ahead of Chicago in winter and in summer. For a few weeks in March and about a week in late October the gap is 5 hours, because the US and the UK change their clocks on different dates.
Six Hours Most of the Year, Five for a Few Weeks
Chicago is on Central Time, UTC-6 in winter and UTC-5 in summer. London is UTC+0 and UTC+1. When both are on the same season, London is 6 hours ahead. When only one side has switched, it's 5.
The US moves forward on the second Sunday in March, well before the UK does on the last Sunday in March, and the UK moves back on the last Sunday in October, before the US does on the first Sunday in November. In both gaps between the changes, London is only 5 hours ahead.
A quick example. 10:00 AM in Chicago is 4:00 PM in London most of the year and 3:00 PM in the 5-hour weeks.
Chicago to London Conversion Table
Each column is one real season of the Chicago-London gap. Pick the column that matches your date.
| 🇺🇸 Chicago (CT) | 🇬🇧 London (CST → GMT) | 🇬🇧 London (CDT → BST) | 🇬🇧 London (CDT → GMT) |
|---|---|---|---|
| 00:00 | 06:00 | 06:00 | 05:00 |
| 03:00 | 09:00 | 09:00 | 08:00 |
| 06:00 | 12:00 | 12:00 | 11:00 |
| 09:00 | 15:00 | 15:00 | 14:00 |
| 12:00 | 18:00 | 18:00 | 17:00 |
| 15:00 | 21:00 | 21:00 | 20:00 |
| 18:00 | 00:00(next day) | 00:00(next day) | 23:00 |
| 21:00 | 03:00(next day) | 03:00(next day) | 02:00(next day) |
- CST → GMT: first Sunday in November to second Sunday in March, while both are on standard time
- CDT → BST: last Sunday in March to last Sunday in October, while both are on summer time
- CDT → GMT: a few weeks from the second Sunday in March, and about a week from the last Sunday in October, when only the US is on summer time
* "next day" / "prev day" = the converted time falls on a different calendar date.
Best Meeting Time for Chicago and London
The overlap is a few hours of the Chicago morning. With 9-to-5 days on both sides, it runs from 9:00 AM to 11:00 AM in Chicago, which is 3:00 PM to 5:00 PM in London, with London's 5:00 PM close as the limit. An 8:00 AM Chicago start (2:00 PM in London) buys an extra hour for London. In the 5-hour weeks the same window is an hour longer.
Avoiding Chicago-London Time Mistakes
London is ahead, so a late evening in Chicago is already the next calendar day in London. With a 6 hours gap, that starts at 6:00 PM in Chicago: 6:30 PM there is 12:30 AM the next day in London. When the gap narrows to 5 hours, the date line moves to 7:00 PM.
Many Chicago calendars show "CT" without saying whether it's CST or CDT. A 10:00 AM CT call is 4:00 PM in London most weeks and 3:00 PM in the short windows. Going the other way, 4:00 PM in London is 10:00 AM in Chicago normally and 11:00 AM in the short windows.
A Worked Example: A Chicago Morning Call With London
Suppose a Chicago team calls London at 8:30 AM. In most weeks that's 2:30 PM in London, and in the 5-hour weeks it's 1:30 PM. If London hosts at 3:00 PM, Chicago joins at 9:00 AM in most weeks and 10:00 AM in the 5-hour weeks.
Frequently Asked Questions
What is the time difference between Chicago and London?
London is 6 hours ahead of Chicago in winter and in summer. For a few weeks in March and about a week in late October the gap is 5 hours, when only the US or only the UK is on summer time.
What time is 9 AM in Chicago in London?
In most weeks, 9:00 AM in Chicago is 3:00 PM in London. In the 5-hour weeks it's 2:00 PM.
When does the Chicago-London difference change?
The US moves forward on the second Sunday in March, before the UK does on the last Sunday in March, so the gap drops to 5 hours in between. In autumn the UK goes back on the last Sunday in October, before the US does on the first Sunday in November.
What is the best time to schedule a Chicago-London call?
Chicago morning. 9:00 to 11:00 AM is 3:00 PM to 5:00 PM in London most of the year and 2:00 PM to 4:00 PM in the 5-hour weeks.