I have written a library that provides commands to read event data from the users calendar on MacOS and iOS. I have no way of knowing if the library works on iOS as I do not have room for Xcode on my machine.
I will attempt to attach a LCB library .lcb and a test application that runs on macOS Big Sur. Failed! Dropbox links below.
If you are willing to run some tests then please run the built application which may be downloaded from my dropbox. The recent issue that I struggled with is one of requesting authorisation from the user for the application to access calendar events. Please note that the application will also request access to your contacts as calendar and contacts work hand in glove.
To run a test :
1. Run the test application. 2. Choose the start and end dates.
3. Press the button "Populate Data Grid with Events".
This action should cause MacOS to prompt for permission to access both Calendar and Contacts and then if granted it will return an array of Events data which should populate the datagrid. When complete the application should be listed in your privacy pane. The log panel may give me some idea of what is going wrong should the application fail.
4. From this point on you should be able to request event data that falls between two dates.
5. The button "Remove App from System Privacy Settings" does exactly that and allows you to run multiple tests from the same start position.
6. I enclose the .lcb file so that you may review it to confirm you are happy it is not attempting to empty your bank accounts or run off with your first born

Download Test Application : https://www.dropbox.com/s/aqh3zjwstp45v ... p.zip?dl=0
Download Library that app uses for review : https://www.dropbox.com/s/1lrtvycaygp89 ... b.zip?dl=0
Thanks, I await your comments,
Simon