From the ALA website:
Celebrate National Library Week 2015 (April 12-18, 2015) with the theme "Unlimited possibilities @ your library®."
First sponsored in 1958, National Library Week is a national observance sponsored by the American Library Association (ALA) and libraries across the country each April. It is a time to celebrate the contributions of our nation's libraries and librarians and to promote library use and support. All types of libraries - school, public, academic and special - participate.