Moodle will be unavailable from 6:00 a.m. to Noon on Thursday, May 17 while OIT performs a scheduled upgrade to Moodle 2.2.
This new release will provide Moodle users with a few new features, enhancements to the user interface, and security improvements.
For details see:
http://docs.moodle.org/dev/Moodle_2.2_release_notes