Does the time difference between New York and Stockholm change during the year?

Yes. Because of daylight saving time the gap moves between −6h and −5h.

When is the best time to call Stockholm from New York?

Between 09:00 and 11:00 in New York, which is 15:00 to 17:00 in Stockholm.

New York is 6h behind Stockholm. This gap is not fixed: daylight saving time moves it between −6h and −5h during the year.

New York

United States

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Stockholm

Sweden

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A 9-to-5 day in each city overlaps for 2h. That is 09:00–11:00 in New York, which is 15:00–17:00 in Stockholm.

City	Time zone	UTC offset
New York · United States	America/New_York	UTC−4
Stockholm · Sweden	Europe/Stockholm	UTC+2

What is the time difference between New York and Stockholm?: New York is 6h behind Stockholm. This gap is not fixed: daylight saving time moves it between −6h and −5h during the year.
Does the time difference between New York and Stockholm change during the year?: Yes. Because of daylight saving time the gap moves between −6h and −5h.
When is the best time to call Stockholm from New York?: Between 09:00 and 11:00 in New York, which is 15:00 to 17:00 in Stockholm.