What is a perpetual calendar?

A perpetual calendar is a calendar that is designed to be used indefinitely without needing to be adjusted. It is different from a regular calendar that needs to be updated every year to account for leap years, the number of days in each month, and changes in the length of the year.

A perpetual calendar is designed to automatically adjust for all of these factors. It keeps track of the number of days in each month, the number of days in a year, and leap years, making it accurate for centuries. It also allows you to determine the day of the week for any date in history.

Perpetual calendars were first developed in the late 16th century, and the mechanism for creating them has evolved over time. Today, they can be found in a variety of forms, including wall calendars, desk calendars, pocket calendars, and digital calendars.

Some popular perpetual calendar designs include the Gregorian calendar, the Julian calendar, and the Chinese calendar. They can be useful for planning events, keeping track of important dates, and for historical research.