Hi, and thanks for your medical question on eHealth forum!
Correct time depends on what you wantâavoid pregnancy or get pregnant. The last 14 days of a cycle are fixed, that is after ovulation, if a woman does not conceive, she bleeds after 14 days. One can also calculate the date (approximate) by subtracting 14 from the average duration of cycle. So in a 28 day cycle the ovulation occurs on 14th day from start of menses, in a 30 day cycle the ovulation will occur on (30-14=16) 16th day of the cycle. The day is counted from the first day of the period. 2-3 days before this day to 2-3 days after the day is the most fertile period. Having intercourse during this time can result in pregnancy. Sperm ejaculated inside the vagina can live for 3-5 days to fertilize the egg. Whereas the ovum only lives for about 24 hours in the fallopian tubes and is available for fertilization. Hence having an intercourse 3-4 days before the expected ovulation date to 2-3 days after the expected date (since the time of ovulation can vary by a day) will help.
Some women get a spotting with ovulation and others get cramps. Almost everyone experiences an increase in white discharge around ovulation. There is always a rise in the basal body temperature (taken first thing in the morning before getting out of bed) around ovulation. Follicular studies by ultrasound can also know the exact date there is ovulation. There are ovulation tests available in market which you can use. Once you do this exercise for a month or two, you can know the safe/fertile period well. Hope this helps. Take care!