Is there a public/government web service that I can call to find out what the national holidays are for a given year? (For the US and/or any country in the world.)
Edit: Does anybody have a set of formulas to calculate US holidays? (C# would be my language of choice if there is a choice.)
There's a web service at http://www.holidaywebservice.com which will provide dates of holidays for the USA, Republic of Ireland, England and Scotland. They also sell a DLL and source code.
As for details of algorithms, you could do worse than check out the excellent Calendrical Calculations book (third edition), which is a really fascinating read for all matters calendrical, and includes sample LISP code for their calendar algorithms.