This application helps you to calculate your ovulation date. It also gives you an estimated fertile period based on the information provided. The following details are required for the calculation; Length of Cycle: this means the date from the beginning of your menstrual flow in the current month till the date of the beginning of menstrual flow for the next month. This value must have been observed to be consistent for a long period of time. Date of the first day of your last menstrual period