Abstract: Incorporating for the first time in a perpetual calendar the concept of separating the two digits of the "year," into a single DEACDE digit plus a single YEAR digit, this device determines the calendar for any desired century, decade, year and month whatever, by positioning these calendric time units in combination with each other in successive chain-like liaison, automatically revealing, as a result, the correct calendar desired. It consists of a number of components, each comprising one or more indicia-group-bearing and viewing-area-embracing means or elements (of whatever kind, style or nature), each of which consists either or an indicia-group region and a viewing-area (fenestella, arrow, or the like) region, or of two indicia-group regions. The desired century can, in a given calendar, be displayed in only one way; this determines the only single way in which the desired decade can then be displayed, this positioning, in turn, determining uniquely the spatial setting of the desired year, and so on.