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

Yes. Because of daylight saving time the gap moves between +7h and +8h.

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

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

Nairobi is 7h ahead of New York. This gap is not fixed: daylight saving time moves it between +7h and +8h during the year.

Nairobi

Kenya

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New York

United States

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A 9-to-5 day in each city overlaps for 1h. That is 16:00–17:00 in Nairobi, which is 09:00–10:00 in New York.

City	Time zone	UTC offset
Nairobi · Kenya	Africa/Nairobi	UTC+3
New York · United States	America/New_York	UTC−4

What is the time difference between Nairobi and New York?: Nairobi is 7h ahead of New York. This gap is not fixed: daylight saving time moves it between +7h and +8h during the year.
Does the time difference between Nairobi and New York change during the year?: Yes. Because of daylight saving time the gap moves between +7h and +8h.
When is the best time to call New York from Nairobi?: Between 16:00 and 17:00 in Nairobi, which is 09:00 to 10:00 in New York.