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I managed to get my iPhone and iPad to update by switching region from UK to Ireland, going into the Calendar app and waiting for the UK Holidays calendar to change to the Ireland one (just a few seconds) then switching region back to UK, whereupon it switched back to the UK Holidays calendar populated until 2025.
 
Users in Australia, the UK, Spain, Germany, Portugal, Sweden, Denmark and other countries are not seeing holidays for their country show up in the Calendar app.

Holidays are showing up appropriately in the United States so this is not a worldwide issue

Errr excuse me MR but when did the United States become the centre of the universe? At the time of the issue being reported the issue was noted to be found in multiple countries in the world which would constitute a world wide issue but because the issue has not occured in the United States, regardless of the fact the issue has been reported to affect user in numerous countries around the world, it's not considered a world wide issue. Therefore MR, please tells us what does constitute a 'world wide issue' and please do not use the excuse 'we just copied from the original article' because your supposed to be reporters who are supposed to read and understand what they are reporting on, not just parrot phrase a 3rd party article and post it verbatim.
 
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