Scheduling and managing events using Outlook.com calendar
When you add national holidays in Outlook, it may create a separate calendar for those holidays instead of adding them directly to your existing calendar. This behavior is typical for Internet calendars, where the calendar subscription is managed separately and does not integrate directly into your main calendar view.
To manage how holidays are displayed, you might need to check your calendar settings or the specific method you are using to add the holidays. If you're using Outlook Web Access (OWA), the server manages the calendar subscription, and updates may sync periodically, which could also affect how they appear in your Outlook desktop application.