How to create a shared company calendar for time off and holidays?

I can offer an update but I'm not 100% confident about it.

It seems like I can create and manage calendar events for Groups and SharePoint sites but not for a Team. All of our Groups are in Teams so I *think* the calendar only works if you create a Group then migrate it to a Team.

So, if I'm Outlook online and I go to People/Groups that I own or manage, this is the list of 'things' I can use for Calendars. I don't see any Teams here so I can't use them for Calendars (not cool).

I have a Company Calendar from a Sharepoint site (domain.sharepoint.com/sites/CompanyCalendar). I can put Thanksgiving on the calendar and this shows up in Calendar under Groups > Company Calendar. I can also drop this calendar into any(?) SharePoint site/page using the Calendar widget. I have this widget on our main Sharepoint site for everyone to see upcoming paid holidays.

In your case, provided each of your departments has their own Group or Sharepoint site, you should be able to do the same. So maybe on your Sales Department site you'd have the Sales Department Calendar and also the main Company Calendar.

I'm not seeing a good way to combine or collate calendars. Ideally, there would be one calendar showing holidays, closures, corporate events, PTO requests, etc. I haven't looked into it but I'm wondering if a unique Group (All Calendars) can subscribe to all these calendars so it could be displayed in a comprehensive SPO site widget.

Would love to get some feedback from anyone who could investigate these findings on their end.

Oh - I'm just re-reading my original post. I've completely given up on integrating with Apple products LOL. From my perspective, the calendar is available only in Outlook and a SharePoint widget.