Daysy: the fertility tracker you can trust

Daysy has been developed as a medical device. Not every fertility tracker on the market meets the standards required of a medical device, which are controlled and regulated by a quality management system. Daysy’s precision and quality are our highest priority.

Switzerland-based Valley Electronics AG, creator of Daysy, is certified according to EN ISO 13485, meaning that our quality management is oriented toward the latest standards for medical products. All procedures at Valley Electronics AG are regularly subjected to internal and external overview. This allows us to continuously improve on and innovate our family of fertility trackers.

Valley Electronics AG is registered with the FDA and is required to comply with medical device regulations that are subject to regular inspections by the FDA in our Zurich office and suppliers. Furthermore, our quality management system is audited yearly by an independent European Notified Body.

The unique Daysy algorithm

Daysy determines your fertile and infertile phase using an extensive database and proprietary algorithm. Based on five million menstrual cycles and an algorithm that draws on knowledge from more than 30 years of research, including several studies, Daysy can give you reliable information about your menstrual cycle.

The accuracy of the algorithm used by Daysy has been systematically tested. For the scientific study, 107,000 cycles (basal temperature, menstrual input) of 5,328 women from Germany and Switzerland were evaluated over a period of ten years.

The independently reviewed result shows that Daysy has an overall accuracy of 99.4% in distinguishing between non-fertile and fertile days.

For more Information please click: 

Daysy Clinical Trial 2021

Just 0.6% of the days displayed were green, although they were in the fertile window and thus should have been "red" (possibly fertile) (see graph). However, 50% of these "false green days" were five days before ovulation and thus have only a minimal chance of pregnancy during this period.

Accuracy (EN).jpeg


The algorithm is created by combining three elements - the acquisition and learning of new data (your daily basal body temperature, start and end of menstruation, and accumulated past cycle data) and statistical analysis (e.g. the temperature rise that occurs after ovulation).

After a learning period, during which Daysy gathers your personal data, the algorithm begins to predict your ovulation and can open your fertile window (red days) at least five days before the earliest possible date of ovulation (figure 1 A). Once a rise in basal body temperature is registered and the algorithm can confidently recognize ovulation, Daysy will show you subsequent individual infertile (green) days until the next menstruation (figure 1 B).

Daysy Algorithmfigure 1 A

Fertility Tracker Method_B-EN.pngfigure 2 B

In the background, the algorithm takes into account the previous average temperature for each measurement, so it is also possible to tolerate occasional outliers or measurement failures. If Daysy does not have sufficient data to deliver a red (possible fertile) or green (infertile) indicator, Daysy will display a yellow (learning/cycle fluctuation) indicator and remember the fluctuation for the coming cycle.

In short, Daysy learns!

Tracking BBT: a few degrees make the difference

Daysy uses a very sensitive sensor to measure the basal body temperature. The sensor’s most unique feature is that it waits for the mean temperature value, which can take up to 60 seconds.

The sensor warms up before it records your basal body temperature in order to receive an accurate result. Daysy waits until the final temperature value has stabilized to complete the reading. If the temperature drops during the measurement (for example, due to cold air that gets into the mouth through breathing), the sensor waits for it to rise again and stabilize. This unique feature differentiates Daysy from less sophisticated basal body thermometers.

This method of temperature tracking ensures that the measurement is as precise as possible.

Thermometer vs Thermosensor (EN) .jpeg


Our goal: accuracy and quality

Valley Electronics AG is a pioneer in the field of fertility trackers. We have developed, innovated, and improved on fertility tracking technology for over three decades. We have 500,000 users worldwide who can attest to the accuracy and quality of our devices. 
We have history and longevity, but we are also on the cutting edge of femtech for fertility. Daysy was the first fertility tracker to be combined with a companion app. Our updated tracker, Daysy 2.0 is the 2019 winner of the Red Dot Design Award. 

We strive to create the best fertility trackers on the market and be a leader in our industry. That is why we continuously work to optimize Daysy. We always endeavor to find the best solution for our users. Going forward, we will continue to spare neither cost nor effort to make sure that you are always happy with Daysy.

Daysy - Your personal fertility tracker (incl. app DaysyDay)
299.00 EUR

incl. VAT and Shipping - Product available - Delivery time: 2-3 days*

Daysy is an intelligent fertility tracker that lets you get to know your very own menstrual cycle.