In five years of working at a Jewish-sponsored university, I've learned that two things are taken very, very seriously: kosher food laws, and holidays/Sabbaths. April and September-October bring days off -- some years, like this year, a lot of them.
I tend to spend these bonus days doing research. During Passover I shut myself up at the UNLV library, listening to oral histories (on a tape recorder!) and going through archives of the Sun and the Review Journal. Neither newspaper is indexed, so I had to read them page by page, which was extremely distracting (pause to see how different "Rex Morgan, MD" was in 1964 (not very)...pause to read prices of stereos and Danish Modern furniture...pause to consider a picture of LBJ and Khrushchev in fake Beatles wigs.) I think I got through about 2 weeks of February 1964, all told.
I started this set of holidays by going to the Museum of Atomic Testing. Atomic testing is emerging, maybe, as a motif in the book. It opens with one of my protagonists remembering watching atomic tests from the playground of her elementary school, and the other protagonist has a father who works at the Test Site. It's an interesting museum, combining serious information with some atomic kitsch. (The old "Duck and Cover" movie is played.) I noticed that the sections devoted to the later underground tests attracted much less attention from the visitors. I tried to look at everything, though I didn't find much information on workers at the site. (There's also a reading room and a public archive, which I might go back to later if I have more specific questions.)
There's a fine line with research. Too much can drag you down, quell the imagination. But finding that odd gem of a detail gives the book authenticity. When I come away from the research library, heavy-headed and a little sleepy, I'm usually aware that somewhere in my notebook is something that will lead me in a direction I never thought of.