Hi @J. Close,
TODAY, all of a sudden, every time I select a cell with a date (in Excel) to copy, I get a pop-up message asking if I want to create a calendar event.
Does the issue persist even if you create a new Excel workbook and entering date in some cells?
Based on your description, I tried testing in my Excel for Microsoft 365 (current channel) but didn't see any pop-up when selecting or copying a cell with date. I've also did a quick search in the release notes for Micrsoft 365 apps but didn't see any new features which could be related to this pop-up.
Given this. could you collect the detailed build number of your Excel application via File > Account > Excel so that I can try searching or testing further on this?
Besides, in order to help narrow down if it's related to any add-ins, it's suggested to follow the steps below:
- Go to File > Options > Add-ins, select "COM Add-ins" > Go.

- Clear the checkbox of all add-ins.
- Reopen Excel and see check the result. If it works fine, you can try re-enabling add-ins one by one to find out the culprit.
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