I have started taking flax seeds from first day of my period but it really worsen my condition. (nicolejardim.com)
It's also in the scriptures that you need to sacrifice a pigeon on the first day of your period. (religion.blogs.cnn.com)
According to Mayo clinic, ovulation occurs around the 14th day of your menstrual cycle (day 1 is the first day of your period), it is thus possible to determine the day that you are likely to ovulate. (intelligentmother.com)