I have Outlook 2003 on several of my computers and found that on one there was no entry for Memorial Day this year which is on the 26th of May. Funny, isn’t it, maybe you have the same problem. I found that Office 2003 may not be showing the holidays past 2007.
I found a fix at Microsoft. In my case, I was not able to just install the update. I have to change the outlook.hol file to outlook.old, remove all of my loaded holidays from within Outlook, download the update for holidays to 2012, and then re-enable holidays in Outlook all over again.
It sounds complicated, but is not really. Just click my post title to read the instructions, get the download link, and follow step by step instructions.
If you are not sure if you have a problem, go to July 4th in your calendar. If you don’t see the Fourth of July holiday listed you have the same problem as I did. In my case even having Office service pack three did not resolve the problem. My computer was up to date, but the holidays had simply not loaded and reverted back to the old holiday file. Microsoft addresses this specific issue in the link and exactly how to fix it.