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36 Years Ago Developed by

Dr. Rechberg

Technology you can rely on

Daysy meets the requirements for a medical device. Precision and quality are our top priority.

Valley Electronics AG, based in Switzerland and manufacturer of Daysy, is certified according to EN ISO 13485. All procedures at Valley Electronics AG are regularly audited internally and externally.

Valley Electronics AG is registered with the FDA. The FDA inspects our Zurich office and our suppliers. Our quality management system is audited annually by an independent European Notified Body.

Daysy's Unique Internal Algorithm

Thanks to the internal algorithm in Daysy, your cycle can be calculated quickly and accurately in real time. The algorithm is based on 5 million menstrual cycles and learns your personal cycle, even if your current cycle is different. Gain insight into your cycle.

Valley Electronics produces the Daysy®, LadyComp® and Teena®

Safely monitoring your own cycle has been around since 1986

Proof Through Science

The accuracy of Daysy's internal algorithm has been systematically tested. For the scientific study, 107,000 cycles (basal body temperature, menstrual input) of 5,328 women from Germany and Switzerland were evaluated over a period of 10 years.

Couple satisfied with fertility tracker Daysy

Independently Assessed Result

99.4% accuracy

When calculating fertile (red) days, Daysy is 99.4% accurate.


For more information:

Publication of the study .

Fact Sheet Study .

Scientific research with fertility tracker Daysy


In 40 Countries

Sold in 40 countries, Daysy is very popular

Daysy is used in 40 countries worldwide.

View the list of countries.

Daysy around the World

Gain insight into what your body is currently showing and how your current cycle is progressing in real-time. You can see how the basal body temperature (BBT) is displayed and how ovulation is recognized. BBT temperatures are determined by the different hormones active during your cycle. This creates a difference between the temperatures before and after ovulation.

The internal algorithm takes previously measured temperatures into account to identify outliers and/or measurement errors. Measure consistently and confirm the menstrual days. If you are less consistent, Daysy will give you the yellow color first to get to know your cycle before showing the red (possibly fertile) or green (infertile) color.

Real-Time Information

menstrual cycle before and after ovulation
Daysy sensor is very accurate, measurement errors are excluded

Daysy has a very sensitive sensor to measure basal body temperature. The most unique feature of this sensor is that it waits for the average temperature value, which takes 90 seconds.


The sensor heats up to get an accurate result. Daysy waits until the final temperature value has stabilized to complete the measurement with the 'beep beep' sound. If the temperature drops during the measurement (for example due to cold air entering the mouth through breathing), the sensor waits until the temperature rises again and stabilizes. This unique feature sets the Daysy apart from less advanced basal body thermometers.

Measure under the tongue

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