Cycle Day 1 is the first day of your menstrual period. The last day of your cycle is the day before your next menstrual period starts. The average cycle length is considered 28 days, but many women have longer or shorter cycles and it's fine. The average women ovulates approximately 14 days before the start of her period, but again, that is certainly not carved in stone. The time between your ovulation and period is referred to as a luteal phase. Hope that helps.