try like this buddy @Zahid1
once after getting the date value from the excel with a variable named out_period of type string out_period = “09/10” (make sure that you are getting in this format from excel or if the format changes we need to change the format accordingly while converting to datetime in the below conversion) out_period_DT = Datetime.ParseExact(out_period,“MM/yy”,System.Globalization.CultureInfo.InvariantCulture)
where we have out_period_DT of type DateTime
to increment by one month out_period_DT = out_period_DT.AddMonths(+1)