Microsoft Outlook has a built-in feature to add holidays from different countries and religions to your default Calendar folder. You can add holidays to your Calendar folder by following these steps:
Choose Tools>Options, then click Calendar Options
On the Calendar Options dialog box, click Add Holidays
In the Add Holidays to Calendar dialog box, check the countries or religions whose holidays you want to add, then click OK
For Outlook 2000 and earlier versions, the list of holidays is stored in a text file named Outlook.txt, found in the language specific subfolders of the Office folder. Starting with Outlook 2002, the file is named Outlook.hol.
If you are setting up a company-wide deployment of Outlook, you may want to edit this file in Notepad to add your own holidays, remove lists that you don't want users to import, or correct dates that Microsoft got wrong.
For more information about Outlook holidays and an updated file for holidays through 2007, see: