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

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

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

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

São Paulo is 1h ahead of Toronto. This gap is not fixed: daylight saving time moves it between +1h and +2h during the year.

São Paulo

Brazil

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Toronto

Canada

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

City	Time zone	UTC offset
São Paulo · Brazil	America/Sao_Paulo	UTC−3
Toronto · Canada	America/Toronto	UTC−4

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