SharePoint Lists and Calendar Integration

foulkesatwork,

You cannot use modern calendar list view for your requirements as it only pulls the information from single SharePoint list.

Similarly, you cannot use SharePoint default calendar list web part as well as it can only show the list items from same SharePoint list where the web part is added.

If you need calendar monthly view to show list items from different sites, you cannot achieve it using SharePoint out of the box options.

You can try below two approaches:

1. Create a master SharePoint list with calendar view. Add one Power automate flow for each SharePoint list which will copy list item details from that individual calendar list to master calendar list whenever new item is created or updated. Then you can use the calendar view from master SharePoint list for your requirements.
2. Develop custom SPFx web part which will pull list items from multiple SharePoint sites and show in single calendar view using 3rd party libraries like FullCalendar.
   • Check the calendar web part samples available here: SharePoint Framework Client-Side Web Part Samples & Tutorial Materials 

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