My apologies for taking so long to get back on this. It turns out that the Library of Congress Madison Building (where the National Digital Library Learning Center facility is) is not open on Sunday. Here are the hours:
Monday - Friday 8:30 a.m. - 9:30 p.m.
Saturday 8:30 a.m. - 5 p.m.
If you would like to schedule the next meeting for any of those time slots just let me know.
//Ed