Does the time difference between Dublin and London change during the year?

No. Both cities keep the same local time all year.

When is the best time to call London from Dublin?

Between 09:00 and 17:00 in Dublin, which is 09:00 to 17:00 in London.

Dublin and London are on the same local time. This gap is the same all year — neither city shifts its clocks relative to the other.

Dublin

Ireland

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London

United Kingdom

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A 9-to-5 day in each city overlaps for 8h. That is 09:00–17:00 in Dublin, which is 09:00–17:00 in London.

City	Time zone	UTC offset
Dublin · Ireland	Europe/Dublin	UTC+1
London · United Kingdom	Europe/London	UTC+1

What is the time difference between Dublin and London?: Dublin and London are on the same local time. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Dublin and London change during the year?: No. Both cities keep the same local time all year.
When is the best time to call London from Dublin?: Between 09:00 and 17:00 in Dublin, which is 09:00 to 17:00 in London.