Oh, April 15th is also the day your taxes are due or something.
This story originally leaked when The Verge obtained some documents outlining Google's plan, but Google has since made it official by way of a Google+ post. The sale will start on Tuesday the 15th at 9AM ET, and orders will include either a free sunglass shade or prescription lens frame.
As I noted, this is the Explorer Edition, not a consumer release. Google is looking to once more expand its Explorer program as they have in the past through smaller promotions. Depending on how many sets are available, this likely marks Google's biggest (and last) Google Glass push prior to launch.