Clear duplicated holidays in Outlook

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Solution:

1.   Make sure you are operating inside the calendar then choose View -> Current View -> Events to switch to the table-format Events view. All the holidays will be listed under the Recurrence: (none) group. (Outlook 2003: View | Arrange By | Current View | Events)

2.   Right-click any column heading, then choose Field Chooser.

3.   In the Field Chooser, switch from the Frequently-used fields list to Date/Time fields, and then drag the Created date to the view to add it to the fields displayed. 

4.   Click on the Created column header  to sort by that field.

5.   You should now see two distinct sets of holidays, each in reverse chronological order. Click on the first holiday of the set you want to delete.

6.   Use the scroll bar to view the last holiday of that set. Hold down the Shift key as you click on the last holiday. This selects all the holidays in that set.

7.   Press Delete to remove them all from the Calendar folder. 

8.         Drag the Created column header out of the view to remove it.