Does the time difference between Hong Kong and Lagos change during the year?

No. The gap stays at 7h all year.

When is the best time to call Lagos from Hong Kong?

Between 16:00 and 17:00 in Hong Kong, which is 09:00 to 10:00 in Lagos.

Hong Kong is 7h ahead of Lagos. This gap is the same all year — neither city shifts its clocks relative to the other.

Hong Kong

Hong Kong SAR China

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Lagos

Nigeria

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

City	Time zone	UTC offset
Hong Kong · Hong Kong SAR China	Asia/Hong_Kong	UTC+8
Lagos · Nigeria	Africa/Lagos	UTC+1

What is the time difference between Hong Kong and Lagos?: Hong Kong is 7h ahead of Lagos. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Hong Kong and Lagos change during the year?: No. The gap stays at 7h all year.
When is the best time to call Lagos from Hong Kong?: Between 16:00 and 17:00 in Hong Kong, which is 09:00 to 10:00 in Lagos.