perpetual calendar has double coding for annual and overall transformation, without calculation, reading a year after immediate or future), or gregorienne.

摘要

A perpetual calendar comprises two interdependent tables, each carrying one of two codes pertaining to the years of the Julian and Gregorian calendars. By referring to an accompanying set of codes any day or date can be read off during the current year or past or future years, regardless of the intervening period of time.