Callisto Corporation was a software development company founded by Robert Harris, Mike Barta and in May 1989. Prior to founding the company, all three worked at . They were best known for their series of computer games for the Macintosh in the 1990s, including ClockWerx, Spin Doctor, and . They also were contracted out to work on the software titles Math Blaster, Reading Blaster, and . From 1990 to 1992, they created and expanded Meeting Maker, a networked meeting-scheduling product. In 1991, Callisto sold Meeting Maker to ON Technology.