The Ancient Slavic Calendar built on an ancient hexadecimal system of calculus, 16 years of Circumnavigation pass through 9 Elements, creating a Circle of Life that has 144 years. The beginning of the Circling Years fall on the day of the Autumnal Equinox. On this day, the Great ancient holiday of the New Year began. The Full Solar Circle was divided into three time periods - Autumn, Winter and Spring, and when combined together they give a solar circle - Leto (Summer, if translated literally). Leto lasts 365.25 days, so 15 Years are 365 days, and the 16th Leto is 369 days, that is, 4 days are added to the 16th Leto. This periodicity is called the Circle of Years (15 simple + 1 Sacred Leto = 16 Years), and passing through the figurative nine elements create the periodicity of 144 Leto - the Circle of Life (16 * 9 = 144).The widespread use of the Ancient Slavic Calendar ceased in 1700, when Peter the Great introduced a foreign calendar. The week has shortened to seven days, and the number of months in the year has increased and their names have changed.Our project calls for exploring the Ancient Slavic Calendar and its applications, trying to feel through its cycles and dimensions. At the moment, minimal information on the calendar values is provided. We are actively listening to our users and want to develop the project together with them.