This study, the third in a series of reports, is limited to an analysis of the energy use and cost implications of nine school calendars proposed by the New York State Department of Education. These calendars are characterized as (1) traditional; (2) ten-month school year; (3) mid-August start, two semesters; (4) four-day week; (5) four-day, 7.5 hours; (6) four- and five-day weeks; (7) twelve-month, multiple variations; (8) five eight-week learning periods; and (9) 45-15 rotation. The factors of daily weather, schedule of operation, and building characteristics were combined to simulate the actual operation of the typical school in each climate for each calendar. The magnitude of the variations was small with only the four-day, 7.5 hour calendar producing more than a 10 percent change in all four climates. Given the slight differences between the various calendars observed, the study concludes that it would be difficult to make a strong case for one calendar over the others on the basis of its energy saving potential. (Author/MLF)