If you have your period on April 7, and if your menstrual cycle lasts 28 days, your ovulation date will be April 21st, and your ovulation period will be from April 16th to around April 25th. If you need to calculate the ovulation period based on the time of menstruation, you need to know the time of the next menstrual period. A woman’s ovulation day is usually 14 days before the next menstrual period, together with the first 5 days and the last 4 days counted as the ovulation period. If you have your period on April 7, if your period is regular and your cycle is 28 days, your next period will be on May 5, your ovulation date will be April 21, and your ovulation period will be from April 16 to about April 25th. If you have irregular periods and cannot predict when your next period will come, you cannot determine ovulation based on the timing of your period. For those with irregular periods, you can determine ovulation by using ovulation test strips and taking basal body temperature. The most accurate way is to go to the hospital for ovulation monitoring.