Does the time difference between Madrid and Nairobi change during the year?

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

When is the best time to call Nairobi from Madrid?

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

Madrid is 1h behind Nairobi. This gap is not fixed: daylight saving time moves it between −2h and −1h during the year.

Madrid

Spain

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Nairobi

Kenya

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

City	Time zone	UTC offset
Madrid · Spain	Europe/Madrid	UTC+2
Nairobi · Kenya	Africa/Nairobi	UTC+3

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