Soybean [Glycine max (L.) Merr.] of Maturity Groups (MG) I, II, and III, adapted to temperate environments, are planted at off-season nurseries to reduce the number of years required for cultivar development and genetic research. The objective of this study was to determine the length of time needed for reproductive development of genotypes planted in Puerto Rico throughout the year. The results of the research are needed to schedule planting and harvest activities appropriately. Six cultivars were sown in two photoperiods, natural conditions and under artificial lights to extend day length, during November, February, and June. Days to reproductive (R) stages were determined. Photoperiod had a significant influence on number of days to all R stages, except R8. Average number of days from emergence to full bloom (R2) and maturity (R8) were 39 and 94, and 94 d, respectively, in the lighted environments, and 30 and 88 d, respectively, in the unlighted environments. For each cultivar, number of days to each R stage averaged for all environments was similar. The results indicated that length of the growing season depends primarily on the photoperiod used and that cultivars will grow and develop similarly in plantings throughout the year, regardless of photoperiod and the month in which they are planted.