Hi @Bidoof39
Do you mean you cannot see the country in your country list when using Add Holiday in Outlook client?
I did a test in my environment and we also could not find these countries in the country list. To resolve this problem, maybe you could try to create the custom holiday in your calendar.
1.Open the outlook.hol file (after first making a safe copy of it somewhere else):
For example, it can be here: C:\Program Files (x86)\Microsoft Office\root\Office16\1033\outlook.hol.
2.Go to the end of the file, and add events using the following format:
[Description of Section] nnn - useful description of the section, and then type the name of the events; the nnn part represents the number of events within the section
Event or holiday description, yyyy/mm/dd
Event or holiday description, yyyy/mm/dd
3.On the File tab, click the Options button:
4.In the Outlook Options dialog box, on the Calendar tab, under Calendar options, click the Add Holidays... button
5.In the Add Holidays to Calendar dialog box, select the country and check holidays for it
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