Please note I do google searches to learn the following tricks. Hopeful my tips will reduce a couple of your searches.
Outlook 2003 only has holidays up to 2007. Those devils! You have to search for their hard to find patch or upgrade.
Or you can download this holiday data file and replace the one on your pc.
The file will be located in C:\Program Files\Microsoft Office\OFFICE\1033 or C:\Program Files\Microsoft Office\OFFICE11\1033
The filename is: OUTLOOK.HOL
Make a back up then copy new file to this folder