Daysy is an intelligent fertility tracker that lets you get to know your very own menstrual cycle. Daysy is to be used to facilitate conception and track your cycle. Daysy is not a replacement for contraception.


Certification and research confirm Daysy’s reliability and quality

Daysy has been developed as a medical product. Not every fertility tracker on the market meets these standards. Unlike Daysy, not all were developed as medical products and are controlled and regulated by a quality management system. You can feel confident that Daysy’s precision and quality are our highest priority.


Daysy claims: certification, reliability and precision

Valley Electronics AG, based in Switzerland, has developed Daysy, a medical product that focuses on the woman’s cycle and enables a better understanding of the female body. Valley Electronics AG is certified according to EN ISO 13485, meaning that our quality management is oriented toward the newest standards for medical products. As the customer, you are at the centre of all decisions in product development and manufacturing regarding accuracy and risk. All procedures at Valley Electronics AG are regularly subjected to internal and external controls. This allows us to continuously enhance the quality of the product throughout its entire life cycle.


Fertility Awareness Based Method (FABM)

The term “fertility awareness-based methods” (FABM) refers to different ways of determining fertile and infertile phases of the female cycle and can be used for family planning.

The basis of all fertility awareness-based methods relies on a woman´s understanding and recognition of her fertility! Therefore the exact determination of the fertile and infertile days in a woman’s cycle based on her natural physiological signs. FABM provide couples exact with the information they need to identify the days in each cycle when the woman is likely to conceive.

In doing so, couples know the different phases of the female menstrual cycle in which a pregnancy can occur. Couples can use this information to specifically plan a pregnancy.

There are different ways and methods that women can use to determine their fertility. These include the temperature method, cervical fluid method, calendar method, symptothermal method and symptohormonal method.

As a reliable lifestyle fertility tracker, in the terms of FABM, Daysy calculates the fertile phase of the woman’s cycle based on a very sensitive and precise, computer-assisted basal body temperature measurement, obtained directly after waking up.

Daysy’s integrated thermometer enables a particularly precise measurement. This distinguishes Daysy from other methods which require a separate basal thermometer, leaving it up to the user which thermometer is used: consequently, there is no guarantee that the applied thermometer meets the required standards. Measurement inaccuracies and rounding errors can occur due to the thermometer or when entering the data into the app.


How the algorithm behind Daysy works

Daysy determines your fertile and infertile phase using an extensive database and proprietary algorithm. Based on 5 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.

Due to an intelligent algorithm based on scientific research, many years of experience of more than 500,000 users and a sophisticated technology, Daysy offers highest quality, precision and reliability for fertility tracking. Factors that influence the menstrual cycle, such as phases of stress, alcohol consumption and sleep deprivation, are considered in the algorithm.

The algorithm is created by combining two elements – the acquisition and learning of new data (your daily basal body temperature, start and end of menstruation, accumulated past cycle data) and statistical methods (e.g. the temperature rises after ovulation) that allow prediction of the coming cycle. In this way, it is possible to derive individual infertile (green) days and fertile (red) days after menstruation.

After a learning period, during which Daysy gathers your personal data, the algorithm begins to predict your ovulation and start your fertile window 5 days before the earliest possible date of your ovulation (figure 1 A). In order to determine an increase in temperature by the algorithm, a sustained characteristic temperature increase at the expected time of ovulation is required. If the algorithm has confidently recognized your ovulation, Daysy will show you subsequent individual infertile (green) days until the next menstruation (figure 1 B).

In the background, the algorithm takes into account the previous average temperature for each measurement, so it is also possible to tolerate “outliers” or measurement failures. In order to not take any risks, Daysy will display yellow in the case of doubt and remember the event for the coming cycle – Daysy learns.


A few degrees make the difference

In addition, Daysy uses a very sensitive sensor to measure the basal temperature. Its 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 a reliable 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 method ensures that the measurement is as precise as possible.

Our research

  • Retrospective clinical trial of the electronic fertility indicator LadyComp/BabyComp. [Freundl 1998]

  • Improving usability and pregnancy rates of a fertility tracker by an additional mobile application: results of a retrospective efficacy study of Daysy and DaysyView App. [Koch 2018, retracted]

Statement: The publication of this study was reversed by the journal in which it was published. We would like to comment on this process. Further information can be found here:
If you have any questions regarding this topic, please do not hesitate to contact us at any time.


Daysy: we pursue quality, certification and precision all the way!

We want to offer even more than the current standard. That is why we continuously work to optimize Daysy. Needs and preferences can change during the daily use of Daysy, which is why we always strive to find the best solution for our users. To create and develop a world-class product, attention to detail is just as important as the big picture. In the future, we will continue to spare neither cost nor effort to make sure that you are always happy with Daysy! Our mission is maximum reliability and quality for you!