I really hope they've cleaned up the metatagging in their catalog or this could produce some very misleading results.
For example, if you search America you'll ultimately find a bunch of hits from 1525 due to
this book which was actually printed in 1904.
It apparently got tagged as 1525 because the cover art is an old English primer from 1525.
There are a lot of mistakes like that in Google's metadata. Another problem that was there at one point (I don't know if they've since fixed it) is that individual issues of magazines and other serials were tagged with the date of the first issue. So a 2000 issue of Time magazine might be listed as a 1923 source.