For NC° Birth Control users
The NC° algorithm never changes green and red days in the past for users on NC° Birth Control, even if the estimated ovulation day changes based on the recently added data.
The only case when the algorithm can recalculate a past fertility status is if you go back to edit some past fertility-related data (for instance, if you were to go back and change some temperature data from last month, or add some period data for last week, where there was no period logged previously).
With this in mind, it’s important to always add data in real time and avoid editing your past Natural Cycles data – in particular, period, temperature and LH entries. It’s fine to log other trackers such as symptoms, moods, etc. for previous days, as these trackers don’t have any impact on your fertility status.
For NC° Plan Pregnancy
Because the requirements for NC° Plan Pregnancy are less strict than for NC° Birth Control, the fertility status can change in the past for NC° Plan Pregnancy users.
Each time you log new data, the algorithm will analyze your cycle to pinpoint your fertile window as precisely as possible. A day that was ‘High fertility’ may be adjusted later on to a different status as the algorithm gains more data on your current cycle.