The article considers the calendar reform carried out by Charlemagne against the backdrop of recent debates about the use of the calendar within the framework of Carolingian expansion. The author supposes that there is no need to draw a clear border in the learned time-keeping (astronomically and mathematically informed) and maintains that Carolingian rulers and their entourage, much as their ecclesiastical historiographers, were proud of their Frank origin and consciously sought to adapt the Roman language of power to the realities of the Frank kingdom.