Normally an egg is produced from your ovary 14 days before the start of your next period; if you have regular periods every 28 days then this is also 14 days after the start of your period. There are ways of determining the exact timing of ovulation if you have period cycles that are not regular. The day of ovulation can be predicted by identifying changes in cervical mucus and measuring daily body temperature; there is a slight rise when ovulation occurs. There are now very sensitive urine testing kits available from chemists that enable you to predict accurately the day of ovulation.