The Natural Cycles app provides a daily fertility status displayed as a large colored circle on the Today view, accompanied by descriptive text inside.
Red Days: Use protection
Red Days will be displayed by a red circle, and the words Use Protection on the Today view.
Red Days are days when you may be fertile. On all Red Days, you should use protection (we recommend condoms) or abstain from vaginal intercourse.
The algorithm will give you Red Days to cover your fertile window (six days per cycle) plus some additional days to account for possible variation in your ovulation day from cycle to cycle. Once your window of Red Days has started in a cycle, you will continue to get Red Days until the algorithm confirms your ovulation and that your fertile window has passed.
NC° Birth Control is effective from the first day of use. However, keep in mind that it will take a few cycles for the algorithm to get to know your unique cycle, so you may experience more Red Days in your first few cycles.
In the Calendar view, the Red Days are connected, making it easier for Cyclers (or partners) with color blindness to differentiate the fertile days from the non-fertile days.
Green Days: Not fertile
Green Days will be displayed with a green circle and the text Not fertile on the Today view.
Green Days are days when you are not fertile, which means that you do not need to use additional protection (like condoms) or withdrawal during sex.*
The algorithm will only give you a Green Day if it is certain, based on the data you have logged, that you are not fertile for that day — either by confirming that you have already ovulated or that you are unlikely to do so in the coming five days (due to sperm survival).
You may get your first Green Days as early as in your first cycle. As the algorithm gets to know your unique cycle, you will experience more Green Days. Exactly how many Green Days you get may vary from cycle to cycle, and it will depend on factors such as when you usually ovulate, how much your ovulation varies, and how much your temperature varies from day to day.
You can trust the very first Green Day you are given as long as you see it on the Today view. This means that you have to check your fertility status each day before having sex and not rely on previous predictions.
How long do Red and Green Days last?
Red and Green Days are valid from midnight to midnight the following day. However, your fertility status can change at any time if you add new fertility data, such as a period, temperature, or ovulation/pregnancy test. Therefore, it's important to check your fertility status after logging your data each day.
* Keep in mind that the only method of contraception that protects against STIs is the male and female condom. Should you have a reason for concern, be sure to use them regardless of fertility status.