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

Yes. Because of daylight saving time the gap moves between −5h and −4h.

When is the best time to call Zurich from São Paulo?

Between 09:00 and 12:00 in São Paulo, which is 14:00 to 17:00 in Zurich.

São Paulo is 5h behind Zurich. This gap is not fixed: daylight saving time moves it between −5h and −4h during the year.

São Paulo

Brazil

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Zurich

Switzerland

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A 9-to-5 day in each city overlaps for 3h. That is 09:00–12:00 in São Paulo, which is 14:00–17:00 in Zurich.

City	Time zone	UTC offset
São Paulo · Brazil	America/Sao_Paulo	UTC−3
Zurich · Switzerland	Europe/Zurich	UTC+2

What is the time difference between São Paulo and Zurich?: São Paulo is 5h behind Zurich. This gap is not fixed: daylight saving time moves it between −5h and −4h during the year.
Does the time difference between São Paulo and Zurich change during the year?: Yes. Because of daylight saving time the gap moves between −5h and −4h.
When is the best time to call Zurich from São Paulo?: Between 09:00 and 12:00 in São Paulo, which is 14:00 to 17:00 in Zurich.