The effects of a calendar change from the quarter system to the semester system on enrollment patterns, student credit hour productivity, grading patterns, and course completion patterns were investigated. Enrollment and grade pattern data were collected for nine Florida public universities and Iowa State University, for 1980-1982. Additionally, a comprehensive postregistration survey was conducted at a comprehensive state university. An analysis of the average student credit hour load showed a significant reduction at both the upper and graduate levels after conversion to the semester system. A reduction in the course completion rate also occurred under the semester calendar system, along with an increase in the percentage of course withdrawals. Many students, faculty, and administrators reported that the full-time course load under the semester system had been reduced to 12 hours. The perception that a full-time load was based on the number of courses rather than on the number of credit hours was common among University of Central Florida students. While the ideal calendar is open to question, the findings seem to favor shorter terms such as those provided under the quarter system. (SW)