There are tons of similar information that really should be provided by government web services. It would certainly save a lot of money and errors in the long run if the U.S. Government could provide information like this through web services. Heck, even having it in a downloadable, parseable format would be a big step in the right direction.
I ran across this question while looking for a way to ensure an application skipped all U.S. Federal holidays in working days calculations. The best .gov source I found is:
Operating Status Schedules from OPM
This has the data we need through 2020, but we'll have to type it into our own tables.
