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

Yes. Because of daylight saving time the gap moves between −2h and −1h.

When is the best time to call São Paulo from New York?

Between 09:00 and 16:00 in New York, which is 10:00 to 17:00 in São Paulo.

New York is 1h behind São Paulo. This gap is not fixed: daylight saving time moves it between −2h and −1h during the year.

New York

United States

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São Paulo

Brazil

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A 9-to-5 day in each city overlaps for 7h. That is 09:00–16:00 in New York, which is 10:00–17:00 in São Paulo.

City	Time zone	UTC offset
New York · United States	America/New_York	UTC−4
São Paulo · Brazil	America/Sao_Paulo	UTC−3

What is the time difference between New York and São Paulo?: New York is 1h behind São Paulo. This gap is not fixed: daylight saving time moves it between −2h and −1h during the year.
Does the time difference between New York and São Paulo change during the year?: Yes. Because of daylight saving time the gap moves between −2h and −1h.
When is the best time to call São Paulo from New York?: Between 09:00 and 16:00 in New York, which is 10:00 to 17:00 in São Paulo.