This is actually a couple of days before ovulation, which allows the slower X sperm to get there after the Y sperm have died. Ovulation
can happen when you feel those ovulation
twinges, but if you're timing for a girl, I wouldn't trust that. Those twinges could be due to anything, (gas, follicle getting ready to ovulate, etc). You need to keep track of your cycle with OPKs, Basal Body Temping, Cervical Mucus examinations, etc.