Growth duration and grain and silage yields of corn was studied at eight planting dates. Yield of corn was similar among planting dates upto April 25 for grain and May 10 for silage, but it decreased as planting date was delayed after the critical planting date. The number of days from planting to Bilking varied from 108 to 52 days according to planting dates, but growing degree days (GDD) from planting to Bilking was similar regardless planting dates. Both the number of days and GDD from Bilking to physiological maturity was similar among the planting dates when corn was planted before the above critical planting dates. However, when corn was planted later than the critical planting dates, the number of days from Silking to maturity was extended as planting was delayed although GDD was similar among the planting dates.