Calendar - artworks from mathematics, astronomy and history

The passage of time has always been experienced by humans through the alternation and repetition of day and night, the phases of the moon, and the seasons. The solar day is the basic unit of calendar timekeeping and the shortest of the three cycles that can be directly observed: day, month, year.

At the heart of the book is the fascinating historical development of the calendars in our cultural sphere, as a interplay of mathematics, astronomy, and religion. The most familiar calendars to us are solar calendars, which depict the seasons, such as the Egyptian, Julian, and Gregorian calendars. Additionally, there are calendars that are based on the lunar cycle, like the Islamic calendar. Some of these lunar calendars—such as the Babylonian and Jewish calendars—adjust the lunar year to the solar year through intercalary months.

All the calendar months and years we know contain a specific number of days. Therefore, creating a calendar is an approximation problem with integer solutions. The historical development of the calendar system is presented alongside the astronomical fundamentals and tools from number theory needed for a deeper understanding.

Each chapter consists of a main text and supplementary sections, as well as a problem section. In the latter, most chapters include tasks related to both the main text and the supplementary sections. The accompanying chapter on mathematical tools aids in solving the problems. Detailed solutions are available for download.

The book primarily targets teachers and lecturers seeking inspiration for the fields of physics and mathematics. However, it is undoubtedly also an exciting read for anyone interested in astronomy.