Does the time difference between Cairo and Jakarta change during the year?

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

When is the best time to call Jakarta from Cairo?

Between 09:00 and 13:00 in Cairo, which is 13:00 to 17:00 in Jakarta.

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

Cairo

Egypt

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Jakarta

Indonesia

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A 9-to-5 day in each city overlaps for 4h. That is 09:00–13:00 in Cairo, which is 13:00–17:00 in Jakarta.

City	Time zone	UTC offset
Cairo · Egypt	Africa/Cairo	UTC+3
Jakarta · Indonesia	Asia/Jakarta	UTC+7

What is the time difference between Cairo and Jakarta?: Cairo is 4h behind Jakarta. This gap is not fixed: daylight saving time moves it between −5h and −4h during the year.
Does the time difference between Cairo and Jakarta change during the year?: Yes. Because of daylight saving time the gap moves between −5h and −4h.
When is the best time to call Jakarta from Cairo?: Between 09:00 and 13:00 in Cairo, which is 13:00 to 17:00 in Jakarta.