perpetual calendar(n = noun.group) - a chart or mechanical device that indicates the days of the week corresponding to any given date over a long period of years;

   A calendar that can be used perpetually or over a wide range of years. That of Capt. Herschel covers, as given below, dates from 1750 to 1961 only, but is capable of indefinite extension.

N  chronometry, horometry, horology, date, epoch, style, era, almanac, calendar, ephemeris, register, registry, chronicle, annals, journal, diary, chronogram, clock, wall clock, pendulum clock, grandfather's clock, cuckoo clock, alarm clock, clock radio, watch, wristwatch, pocket watch, stopwatch, Swiss watch, atomic clock, digital clock, analog clock, quartz watch, water clock, chronometer, chronoscope, chronograph, repeater, timekeeper, timepiece, dial, sundial, gnomon, horologe, pendulum, hourglass, clepsydra, ghurry, chronographer, chronologer, chronologist, timekeeper, annalist, calendar year, leap year, Julian calendar, Gregorian calendar, Chinese calendar, Jewish calendar, perpetual calendar, Farmer's almanac, fiscal year, chronological, chronometrical, chronogrammatical, cinquecento, quattrocento, trecento, o'clock.