Does the time difference between Chicago and Rome change during the year?

Yes. Because of daylight saving time the gap moves between −7h and −6h.

When is the best time to call Rome from Chicago?

Between 09:00 and 10:00 in Chicago, which is 16:00 to 17:00 in Rome.

Chicago is 7h behind Rome. This gap is not fixed: daylight saving time moves it between −7h and −6h during the year.

Chicago

United States

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Rome

Italy

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A 9-to-5 day in each city overlaps for 1h. That is 09:00–10:00 in Chicago, which is 16:00–17:00 in Rome.

City	Time zone	UTC offset
Chicago · United States	America/Chicago	UTC−5
Rome · Italy	Europe/Rome	UTC+2

What is the time difference between Chicago and Rome?: Chicago is 7h behind Rome. This gap is not fixed: daylight saving time moves it between −7h and −6h during the year.
Does the time difference between Chicago and Rome change during the year?: Yes. Because of daylight saving time the gap moves between −7h and −6h.
When is the best time to call Rome from Chicago?: Between 09:00 and 10:00 in Chicago, which is 16:00 to 17:00 in Rome.