Time Difference Between Chicago and London

Chicago sits an hour further west than New York, and on this corridor that hour is the difference between a comfortable slot and a squeezed one. With London six hours ahead, 2 PM in London is 8 AM in Chicago and 5 PM in London is 11 AM in Chicago. That three-hour block is where the calls go. Push later and London has gone home; push earlier and Chicago hasn't arrived. Most of the compromise falls on the London side, because anything after their 5 PM eats into the evening while Chicago is still mid-morning. People in Chicago who work with London tend to solve it by starting at 7 AM and treating the first two hours as their overlap.

The six-hour gap is not constant. Chicago moves its clocks forward on the second Sunday of March and London not until the last Sunday of March, so for the weeks in between London is only five hours ahead. The same thing happens in autumn: London falls back on the last Sunday of October while Chicago waits until the first Sunday of November, a one-week mismatch. In those windows a 9 AM Chicago call arrives at 2 PM London rather than 3 PM. Which side feels it depends on how the invite was made. An event created in Central Time holds 9 AM Central and moves for London; one created in UK time holds 3 PM London and moves for Chicago. Audit the recurring ones in early March.

Nonstop from O'Hare to Heathrow runs around eight hours eastbound and closer to nine coming back, when the jet stream is against you. Leave Chicago in the early evening and you arrive at London breakfast time after maybe four hours of poor sleep, at what your body still counts as the middle of the night. That is the expensive direction. Westbound costs you a long day instead of a night: you land in Chicago in the afternoon, stay up to a normal bedtime, and most people work fine the next morning. If the London trip is only three days, put the low-stakes work on day one and the meetings that matter on day two.