Here are the steps to help solve your issue with duplicate events appearing in your Microsoft calendar:

1. Click the View tab on the ribbon.
2. Select Change View, then TimeLine.
3. Drag the vertical Timeline Bar to the left or the right so you can find specific dates.
4. Check the dates to find the duplicates.
5. Remove the duplicate events once you locate them.
6. Mark the duplicate events as Done.

If you are still unable to delete duplicate events, try changing your Microsoft calendar view to Month or List to make it easier to see and delete duplicates.