The ovulation calendar works by looking at a typical cycle, and telling you when ovulation should occur in that typical cycle. Well, that's all well and good for people who have a typical cycle, but a lot of women don't. Even if a woman gets her period every 28 days like clockwork, that still does not mean that she will ovulate when she is "supposed" to.
That's why people who try to use this as a method of birth control often end up with an accidental pregnancy. Some people try to avoid sex during their most fertile time, but some women are actually the most fertile during their period!
So if you are trying to avoid getting pregnant, that's not the best way to go for most people. If you are trying to become pregnant, then it is worth a shot. You can use an online calendar such as
www.mymonthlycycles.com. This site is free and lets women keep track of their period. It will also predict when you should be fertile given your period's habits. It's still not a sure thing since some people ovulate at funny times throughout their cycle. You can also watch for discharge that is clear, stringy, and looks like egg whites. This means you are fertile or will be fertile very soon.
