The Collaborative International Dictionary of English v.0.48:

Perpetual calendar \Per*pet"u*al cal"en*dar\
   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.
   PERPETUAL CALENDARDay of the monthJan. Oct.Apr. July
   Jan.Sept. Dec.JuneFeb. Mar. Nov.Aug. Feb.MayDay of the Week
   18152229abcdefgMon.
   29162330gabcdefTues.
   310172431fgabcdeWed.
   4111825[nbsp]efgabcdThur.
   5121926[nbsp]defgabcFri.
   6132027[nbsp]cdefgabSat.
   7142128[nbsp]bcdefgaSun.

   ===========================================================================
   To find the day of the week corresponding to any date, find
   the small letter directly under the month and opposite the
   day of the month; the same small letter also appears in the
   vertical column that contains the number of the year, and if
   the line in which it stands is followed out to the right, the
   day of the week is found. Thus, the small letter under March
   and opposite 18 is b; b appears again directly over 1904, and
   at its right is the word Friday. March 18 fell on Friday in
   1904, and also in 1898, 1892, etc. The calendar has other
   uses, as for finding the months which begin on Sunday in a
   particular year, etc.
   |1753 |1754 |1755 |1750 |1751 |1757 |*1752
   |1759 |1765 |*1760 |1761 |*1756 |1763 |1758
   |*1764 |1771 |1766 |1767 |1762 |*1768 |1769
   |1770 |*1776 |1777 |*1772 |1773 |1774 |1775
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Perpetual \Per*pet"u*al\, a. [OE. perpetuel, F. perp['e]tuel,
   fr. L. perpetualis, fr. perpetuus continuing throughout,
   continuous, fr. perpes, -etis, lasting throughout.]
   Neverceasing; continuing forever or for an unlimited time;
   unfailing; everlasting; continuous.
   [1913 Webster]

         Unto the kingdom of perpetual night.     --Shak.
   [1913 Webster]

         Perpetual feast of nectared sweets.      --Milton.
   [1913 Webster]

   Circle of perpetual apparition, or Circle of perpetual
   occultation. See under Circle.

   Perpetual calendar, a calendar so devised that it may be
      adjusted for any month or year.

   Perpetual curacy (Ch. of Eng.), a curacy in which all the
      tithes are appropriated, and no vicarage is endowed.
      --Blackstone.

   Perpetual motion. See under Motion.

   Perpetual screw. See Endless screw, under Screw.
      [1913 Webster]

   Syn: Continual; unceasing; endless; everlasting; incessant;
        constant; eternal. See Constant.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Calendar \Cal"en*dar\, n. [OE. kalender, calender, fr. L.
   kalendarium an interest or account book (cf. F. calendrier,
   OF. calendier) fr. L. calendue, kalendae, calends. See
   Calends.]
   1. An orderly arrangement of the division of time, adapted to
      the purposes of civil life, as years, months, weeks, and
      days; also, a register of the year with its divisions; an
      almanac.
      [1913 Webster]

   2. (Eccl.) A tabular statement of the dates of feasts,
      offices, saints' days, etc., esp. of those which are
      liable to change yearly according to the varying date of
      Easter.
      [1913 Webster]

   3. An orderly list or enumeration of persons, things, or
      events; a schedule; as, a calendar of state papers; a
      calendar of bills presented in a legislative assembly; a
      calendar of causes arranged for trial in court; a calendar
      of a college or an academy.
      [1913 Webster]

   Note: Shepherds of people had need know the calendars of
         tempests of state. --Bacon.
         [1913 Webster]

   Calendar clock, one that shows the days of the week and
      month.

   Calendar month. See under Month.

   French Republican calendar. See under Vend['e]miaire.

   Gregorian calendar, Julian calendar, Perpetual
   calendar. See under Gregorian, Julian, and Perpetual.
      [1913 Webster]

WordNet (r) 3.0 (2006):

perpetual calendar
    n 1: a chart or mechanical device that indicates the days of the
         week corresponding to any given date over a long period of
         years