The most commonly used calendar cycles are described in this paper, with a focus on the advantages and disadvantages of each. Calendar options include the following plans: 45-15 block and staggered, flexible 45-15, 60-20 block and staggered, 90-30 staggered, Concept 6, 60-15, Concept 8, trimester, quinmester, Concept 16, Concept 12, multiple access, flexible all-year, and personalized continuous year. Four variations that have not been implemented are also described: the Living Learning System; Flexi-Term Plan; Concept 7 or 9 Plan; and additional modifications. Fifteen figures and attendance patterns of the various tracks are included. National statistical summaries of public schools engaged in year-round education for the years 1990-91 and 1991-92 are presented. (LMI)