Biorhythms – the idea that natural biological rhythms influence our physical, emotional and mental well-being – caught on in the late 1960s, capturing imaginations and inspiring Certina to create the Biostar: the world's first watch to display a person's daily biorhythms on the dial. Three main biorhythmic cycles were believed to impact everyday life: the physical cycle, lasting 23 days; the emotional cycle, 28; and the mental cycle, 33 days. Although each person's biorhythms varied, once the Biostar's biorhythm-mechanism had been set to reflect the wearer's date of birth, it tracked the three main cycles and displayed them on the dial.
The first Biostar debuted in 1965 with a mechanical movement and a built-in biorhythmic mechanism. Certina's engineers developed a more advanced version, the Certina Biostar Electronic, which premiered for in 1971 at the MUBA fair in Basel, a showcase for innovative and creative technologies. The new Biostar displayed the physical, emotional and mental biorhythmic cycles in red, blue and green, respectively. It enjoyed success in Switzerland, Japan and Australia, and new versions were released in the years to follow.