Are you using MS Outlook? Bummed that it doesn't list holidays by default? Don't add them manually! In Outlook 2003 (and indeed back to Outlook 97), you can get it to recognize holidays (in any of several countries) with just a simple button. The trick is knowing it's even there!
Here are the steps in Outlook 2003. It's only slightly different in earlier editions: while viewing the inbox (or calendar), use the "Tools" menu to choose "Options". In the window that opens, the first tab ("Preferences") is selected automatically. In its "Calendar" section, choose the "calendar options" button. In the window it opens, the second section is also labeled "calendar options" and it has an "add holidays" button. Click that, and it opens a selection box of supported countries whose holidays it can show. It pre-selected the US for me (perhaps it detects your Windows locale setting), and I assume you could select more than one country. Click "ok" and it will add the holidays. Sweet!
You see the names of the holidays fly by (there were many of them), and it seems more than just the core federal holidays. Anyway, you can surely delete any you don't care to keep.
Some additional info for those intrigued:
Actually, it's quite easy to see what dates it adds. Again the steps in Outlook 2003 are as follows (and earlier editions are only slightly different). In the calendar view, use the "View" menu, choose "arrange by" then "current view", then "events". you can click the "category" column to sort, and see those listed as "holiday". You can select any of them to delete.
You can also see the file which Outlook uses to get the holidays. Again, in Outlook 2003, look for a file named outlook.hol in C:\Program Files\Microsoft Office\OFFICE11\1033\. You'll see it's a text file that holds holidays for each country, and within country by holiday, and then for each holiday it shows the dates in 2003-2007. In editions prior to Outlook 2002, it was called outlook.txt.
Finally, while looking for some additional resources to point you to, I found this cool site that addresses several issues you may run into with respect to holidays in Outlook, particularly in supporting corporate settings, as well as info on updated holiday date files available from MS to correct mistakes. See http://www.slipstick.com/calendar/holidays.htm
Hi:
I'm afraid I have no other thoughts. Please look at all the info above in
detail, including the link to the slipstick site that helps address issues.
There may be clues in both places to help you. I really have nothing more
to offer other than to suggest that you may want to close and reopen
Outlook to see if things take effect then. Sorry that I can't offer any
more.