We determined the impacts of calving season length on net returns and variability in net returns for spring-and fall-calving herds in Tennessee. Weaning weight as a function of calving date was estimated using a 19-year data set and simulation models generated distributions of net returns for 45-, 60-, and 90-day calving periods with and without using hypothetical improved reproductive management (IRM) practices. Shortening the calving period from 90 days increased expected net returns in the spring-and fall-calving herds. The 45-day fall-calving period with IRM maximized profits, but an extremely risk-averse producer would select a 45-day fall-calving period without IRM.