As part of a comprehensive study of all mandates placed by the state of Illinois on elementary and secondary education, an analysis was undertaken of the school day/school year mandate in its historical perspective, inquiring into its original purpose, how well that purpose has been served, whether the mandate is still needed, and whether a differently defined or implemented mandate would yield the desired result. The study revealed that since 1959 (when the minimum required daily instructional time was extended to 5 hours), the substantial increase in new instructional mandates and ancillary educational services, reflecting a common belief in education as a vehicle for social change, has imposed a burden on school time allotments, as new programs necessarily displace time previously devoted to the basic purposes of schooling. Accordingly, an increase in the school day or school year in itself will not guarantee improved student achievement. Rather, the state should define the academic core of instruction, mandating five hours each day for language arts, foreign languages, mathematics, science, and social studies (including history), while adding two hours to accommodate other instructional services. Appendixes are provided, including statutes, regulatory references, and selected statistical data. (TE)