Before your ovulation is confirmed
The algorithm will make a prediction for your upcoming ovulation day in each cycle based on your historical data, such as when your ovulation usually occurs and how much this varies from cycle to cycle. You can view your own average ovulation day and variation in the My Cycle tab.
The predicted ovulation day will be shown in your graph with a grey ovulation symbol, and the predicted ovulation window will be displayed as a grey field on the surrounding days.
After your ovulation is confirmed
When the algorithm has confirmed that your ovulation has occurred in the ongoing cycle, it will calculate the most likely ovulation day from the temperature curve. If the algorithm is not able to narrow down one specific ovulation day based on the data added, it will provide a window of several days, within which your ovulation most likely happened.
This ovulation window will be displayed as a purple field in your graph, and the most likely ovulation day will be marked with the ovulation symbol.
As you continue to add more data during your cycle, the algorithm may also come to recalculate the day you most likely ovulated if your newly added data supports this.
If the algorithm does not have enough data to narrow down the exact ovulation day before the end of the cycle, it will be able to do so once you start a new cycle. Since your luteal phase usually remains rather stable from cycle to cycle (although the length can vary from person to person), your average luteal phase length gives some additional information about the timing of your ovulation.
When a new cycle starts, the algorithm will go over all the data for the past cycle one more time and also consider your luteal phase. It will then be able to narrow down the ovulation window to one specific day considering both the temperature curve and your average luteal phase length.