Not possible unless you have write access to all the folders and want to
write code. See http://www.outlookcode.com/d/forms/holiday.htm for
semi-automatic solutions.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> How I make automatically to add to the holidays in the calendar of all the
> users?