Book excerpt: Calendars of Mesoamerican civilisations are subjected to what is categorised as “ritual practices of time”. This book is a comparative explication of rituals of time of four calendars: the Long Count calendar, the 260-day calendar, the 365-day calendar and the 52-years calendar. Building upon a comparative analytical model, the book contributes new theoretical insights about ritual practices and temporal philosophies. This comprehensive investigation analyses how ritual practices are represented and conceptualised in intellectual systems and societies. The temporal ritual practices are systematically analysed in relation to calendar organisation and structure, arithmetic, cosmogony and chronometry, spatial-temporality (cosmology), natural world, eschatology, sociology, politics, and ontology. It is argued that the 260-day calendar has a particular symbolic importance in Mesoamerican temporal philosophies and practices.