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

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

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

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

Madrid is 6h ahead of New York. This gap is not fixed: daylight saving time moves it between +5h and +6h during the year.

Madrid

Spain

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New York

United States

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

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

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