There is a very limited window in which conception can occur.A fertile egg has a lifespan of 24 hours once released from the ovary at ovulation andsperm have a lifespan of around 23 days.Therefore your most fertile days fall 2 days before and 24 hours after ovulation.nnSo how do you know when youre ovulating?nnYour Zycia Personal Ovulation Calendar willnPlot your temperature on a graph, highlighting your most fertile daysnProvide an alert on your most fertile daysnPredict your future fertile days nKeep records of previous cycles and graphs to help establish your fertility pattern