The key notion for modelling calendar systems as well as many periodic events, for example the seasons, is the notion of a partitioning of the real numbers. A partitioning of R splits the time axis into a finite or infinite sequence of intervals. Basic time units like seconds, minutes, hours, days, weeks, months, years etc. can all be represented by finite partitionings of R. There are a lot of other temporal notions which can be modelled as partitions either: the seasons, the ecclesiastical calendars, financial years, semesters at universities, the sequence of sunrises and sunsets, the sequence of the tides, the sequence of school holidays etc. In this paper a formalization of periodic temporal notions by means of partitionings of R is presented.

The paper is limited to 4 pages. Therefore it contains only basic ideas and informal descriptions. The technical details can be found in [9].