Abstract: A perpetual calendar possessing the ability to display any date, past, present or future, in a finite range, and the day of the week for that particular date without prior knowledge or calculation, includes individually gear driven indicia belts for composing month and year dates and another indicia belt which is simultaneously gear driven with the movement of any one of the aforesaid indicia belts. A single drive gear for the aforesaid individually gear driven indicia belts is shiftable into driving engagement with a selected indicia belt by linear movement of a sliding indicator on the top panel of the calendar housing. The drive shaft for the single shiftable drive gear is turned by an external knob on one side of the calendar housing.

Abstract: A calendar utilizes an existing relationship binding together all dates, past and future, in relation to any starting date. The constant relationship between days of the week, months of the year, and numbers enables the user of the calendar without resorting to calculation to find and display any other date not known in advance by simple manipulation of moving components of the calendar. For any given date as a reference point, one may determine, for example, the day of the week of any past or future date without prior knowledge or calculation over the full range of dates encompassed by the calendar.