How-to guide
England and Wales bank holidays are built into Metre2 Calendar. With Calendar Pro you can add the others in one click - Scotland and Northern Ireland from GOV.UK's own calendars, the public holidays in Ireland and the UK clock changes - and they keep themselves up to date.
Click + Bank holidays and more in the sidebar.

Click Subscribe next to Bank holidays - Scotland. Calendar fetches GOV.UK's calendar, with one-off holidays when they're announced.

Irish public holidays (St Brigid's Day included) and the UK clock changes are worked out by Calendar itself.

They show next to your own events, read-only, in their own colours.

Untick it in the sidebar to hide it, or open the panel and click Remove.

Yes, built in and free. The GOV.UK subscription adds one-off holidays that can't be predicted.
Yes - Calendar Pro has a 7-day free trial in the app.