This is one of the first major discoveries of underwater archaeology: a calculating device. According to some researchers, it was used to determine and predict important astronomical events. Its remains were found in the early 19th century by sponge fishermen near the island of Antikythera. It was probably assembled in a workshop in Rhodes, Syracuse or Asia Minor at the end of the 2nd century BC. It has a complex mechanism consisting of at least thirty-five cogwheels driven by a crank. The Antikythera machine is the oldest known gear mechanism. Its reconstruction includes two plates showing several graduated circles. Our article focuses on one of these circles, which contains 30 symbols, presumably to represent a month in the Egyptian calendar