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

Yes. Because of daylight saving time the gap moves between −9h and −7h.

When is the best time to call Melbourne from Cairo?

Between 09:00 and 10:00 in Cairo, which is 16:00 to 17:00 in Melbourne.

Cairo is 7h behind Melbourne. This gap is not fixed: daylight saving time moves it between −9h and −7h during the year.

Cairo

Egypt

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Melbourne

Australia

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

City	Time zone	UTC offset
Cairo · Egypt	Africa/Cairo	UTC+3
Melbourne · Australia	Australia/Melbourne	UTC+10

What is the time difference between Cairo and Melbourne?: Cairo is 7h behind Melbourne. This gap is not fixed: daylight saving time moves it between −9h and −7h during the year.
Does the time difference between Cairo and Melbourne change during the year?: Yes. Because of daylight saving time the gap moves between −9h and −7h.
When is the best time to call Melbourne from Cairo?: Between 09:00 and 10:00 in Cairo, which is 16:00 to 17:00 in Melbourne.