Calendaria

Calendaria is a proposed civil calendar and timekeeping system designed to regularize the year by dividing it into 13 months of 28 days each, for a total of 364 days. To bring the calendar into alignment with the solar year, a Year Day is added outside the weekly cycle, and in leap years an additional intercalary day is inserted. The concept appears in discussions of calendar reform as a means to improve predictability in planning, scheduling, and data organization.

Structure and rules: Each month consists of four weeks of seven days, so months are uniformly 28 days long. The standard seven-day week (for example, Monday through Sunday) is preserved, with the Year Day placed outside the weekly cycle as a standalone holiday. In common years the calendar contains 365 days (364 plus the Year Day); in leap years a second intercalary day is added, yielding 366 days. This design aims to produce consistent month lengths while maintaining compatibility with established weekly rhythms.

Naming and cultural considerations: Proposals for Calendaria vary on how to name the months and designate holidays. Common approaches use celestial, seasonal, or natural motifs, with the intent of creating a recognizable and culturally resonant structure. The system is typically discussed as a reform proposal rather than a replacement that prescribes specific traditions.

History and reception: Calendaria has appeared in academic discussions and among enthusiasts of timekeeping reform. It has been explored in digital prototype calendars and classroom demonstrations, but it has not been adopted by any country or integrated into international time standards. Supporters emphasize arithmetic regularity and easier date calculations; critics warn that widespread change would disrupt existing holidays, religious observances, and administrative systems, making large-scale adoption impractical in the near term.

See also: calendar reform, World Calendar, International Fixed Calendar.