The Perpetual Calendar

A helpful Tool to Postal Historians

By Toke Nørby



A Perpetual Motion Wheel!

References to

Printed references (in text referred to as e.g. (1) for "reference 1")

  1. Calender for Aarene fra 601 til 2200 efter Christi Fødsel by Bauer, R. W., Kjøbenhavn 1868.
  2. Udvalgte Filatelistiske og Posthistoriske Artikler, pp 64-71: Posttid by Nørby, Toke. Nørbyhus 1993. ISBN 87-984623-1-8.
  3. Haandbog i Kronologi. I-II by Schroeter, J. Fr. . Cammermeyers Boghandel. Kristiania (Oslo) 1923-1926.
  4. Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit by Grotefend, Hermann. 13. Aufl., Hansche Buchhandlung, Hannover. 1991; ISBN 3-7752-5177-4.
  5. Handbuch der Mathematischen und Technischen Chronologie das Zeitrechniungswesen der Völker by Ginzel, F. K.. Band I-III. Leipzig, J. C. Hinrichs'sche Buchhandlung 1906-1914.
  6. Kalenders by Ahlers, Willy , The Netherlands. De Postzak, No 180, August 1995, pp 221-237. ISSN 0922-7636.
  7. The International Atlas (3rd edition), Shanks, Thomas G. . San Diego: ACS Publications, Inc. (1991), Table II. (Reference from Paul Eggert).
  8. A.D. 1751. Anno vicesimo quarto Georgii II CAP. XXIII: Calendar Act (Out of Order!) by Mark Brader.
  9. Encyclopedia Lituanica - Vol. V. - Boston, 1970, p. 462 and Tarybu Lietuvos enciklopidija. T. 2. - V., 1986. (Reference from Silvija Velaviciene, Head of Department of Lithuanian Publication.)
  10. Ordinance that the 1st of January shall in the future be accounted the first day of the year in Scotland. Holyrood House, 17th December, 1599. (Reference from Angela Lamb).
  11. Salmonsens Konversations Leksikon (Salmonsen's Encyclopedia). Vol. XIII, pp 386-393. Copenhagen 1922.
  12. Handbook of Turkish Philately, Part I, Ottoman Empire: The Calendar. By Andreas Birken. 1995. ISBN 3-932224-00-7.
  13. Dend Nye Af Hans Kongl. Majestæt, Kong Friderich dend Fierde forordnede Almanak for Aar efter Christi Fødsel 1700. The Danish Almanac from 1700. Reprint 1994. Steno Museum. University of Aarhus. Denmark.
  14. Standard C Date/Time Library by Lance Latham (†2008.08.12). SCDTL is published by Miller Freeman: SCDTL (ISBN 0-87930-496-0). SCDTL. (Out of order) Lance has written codes for thirty (30) different calendars - completely solved and interconvertible!
  15. Certificate of Baptism for Nørby, Toke. 1943.07.11 ;-)
  16. Labor in The Soviet Union by Schwarz, Solomon M.. Praeger, New York 1951.(Reference from Inge Marie Larsen, Danish Historian at the State Library in Aarhus, Denmark - with special interest in the history of the Soviet Union, Boris Weil, Russian Historian at the Royal Library in Copenhagen, Denmark).
  17. Entsiklopedicheskii slovar Brokgauz i Efron. Reference mentioned by Maxim V. Kollegov (Aka "Virtual_Max") (Out of Order) and Andrej Shapovalov, Novosibirsk Museum (Out of Order)
  18. Law on Equalizing old and new Calendar dated Beograd (Belgrade) 1919.01.10. (Reference from Branislav Skrobonja).
  19. Jyllands-Posten (a Danish News Paper). Sunday 2000.02.20, Section 1, page 4.
  20. Die Zeit (a German weekly News Paper). No. 1, Wednesday 1999.12.29. (Reference from Manfred Kiefer).
  21. The Muslim and Christian Calendars by G.S.P. Freeman-Grenville. London-Oxford University Press. 1963.
  22. Old Style Dates - New Style Dates and Their Significance by Lowell S. Newman. The Congress Book 1983. Forty-Ninth American Philatelic Congress, November 4-6 1986, pp 191-195.

World Wide Web References: (in text referred to as e.g. (w1) for "www reference 1")

  1. Calendar FAQ by Claus Tøndering.
  2. Error in Statement of Tropical Year (Out of Order) by Simon Cassidy.
  3. Genealogy, Calendars and Dating by James P. Terry. (NB. Terry's page has been removed from the site where I found it, but while it was there, I downloaded a copy - in case you want a copy of this reference!)
  4. Old Style and New Style Dates by Mike Spathaky (New URL 2010.01.26).
  5. Genealogy in France: Republican Calendar by Denis Beauregard. (New URL 2000.04.13)
  6. Russia's Difficulties by Elisabeth Achelis.
  7. "Why can girls propose on leap days?" (Out of Order) by Charlotte S.H. Jensen. Country Archive for Sjælland. (2000.02.24)

E-mail References: (in text referred to as e.g. (e1) for "e-mail reference 1")

  1. Lance Latham. See also (13). Re: Calendar change in Alaska: on the calendar list <> on 1 December 1998 Lance wrote: State Historian Joan Antonson: The October 18, 1867 is Gregorian, and from that date forward the U.S. administered Alaska using that calendar. The pre-1867 Russian records are based on the Julian calendar, as are Russian Orthodox church records for a number of years after the transfer.
        Attu Island is across the international date line. But today no one lives there. Regarding the issue of Alaska being moved across the International Date Line as part of the transfer process, I'm not sure that I follow the question. If the transfer occurred in 1867, and the Washington conference produced the time zone system in 1883, the International Date Line shouldn't have been a problem in 1867. There may have been a less formal agreement about dating in place at the time.

        Re: Calendar Change in Texas: on the calendar list <> on 2 December 1998 Lance cite Galen D. Greaser, General Land Office, Texas: By an order of Philip II dated Sept. 19, 1582, the Gregorian calendar was adopted by Spain as its civil calendar. All contracts, obligations, judicial and extrajudicial acts, correspondence, orders, etc. were henceforth to bear the Gregorian date. Nothing we have seen in Texas documents from the Spanish period indicates anything but strict adherence to the Gregorian reform. We are not aware of any land grant in Texas to settlers from English colonies during the period you reference (1582-1752). (The Spanish colonization of Texas began in th 17th century (11)).
  2. Riina Hallikmäe "Centre of Information Services for MPs" at The National Library for Estonia.
  3. Dik Winter, The Netherlands.
  4. P.H. Honig told me that the Greek Embassy in The Hague had informed him that in Greece the Gregorian Calendar was finally accepted in 1923. 15 February 1923 was followed by 1 March 1923.
  5. Lauri Kreen, Estonia.
  6. Roger Sacco, France.
  7. Peter A. Michalove, USA.
  8. E-mail from 1996.07.08 from Manfred Kiefer to J.P. Terry with reference to (w3).
  9. Branislav Skrobonja, Yugoslavia.
  10. Dan Grecu, Romania.
  11. Amos Shapir, Israel.
  12. Alexandre Galinos, Greece.
  13. Andreas Birken, Germany.
  14. John Harper, New Zealand.
Reccommended Related Calendar References (if referred to in text: e.g. (r1) for "other related reference 1")
  1. The Home Page for Calendar Reform by Rick McCarty.
  2. "The Calendar Zone" Page by Janice McLean. This is the Page where most URL's with calendars can be found.
  3. Today's Calendar and Clock Page by Will Linden. This is also a great collection of calendar information!
  4. The "Revised" Julian Calendar by Christopher Sokolov.
  5. Gregorian Calendar (Out of Order) (How do we Keep Track of Time?) by Albert Van Helden.
  6. Britannica Online (Encyclopedia Britannica, Inc.).
  7. The International ISO 8601 Format Dates by Markus Kuhn.
  8. Marking Time by Lawrence A. Crowl.
  9. The 10,000-Year Calendar. A Nice Online Perpetual Calendar by Justin White.
  10. The Julian and the Gregorian Calendars (Out of Order) by Peter Meyer.
Useful Programs/Sites for Postal Historians - and Genealogists!
  1. Universal Calendar Calculator (Out of order) by Ira Johan Lund, the producer of the Cumberland Family Tree for Windows genealogy program. This Universal Calendar Calculator can display and convert between 10 different calendars: Julian Day Number, Gregorian (New Style), Julian (Old Style), Roman-Julian, French Revolution, Hebrew, Islamic, Chinese, Chinese/Gregorian Thai Suriyakati Calendar. - For postal historians the program is very useful e.g. when you need to analyse the dates in postmarks from various counties.
  2. Calendar Software at The "CalendarLand" Page by Janice McLean. A nice list of free- and shareware calendar programs. Recommendable! (URL changed on 2002.12.03)
  3. Genealogy Resource Index for Denmark (Out of Order) at The Royal School of Library and Information Science, Denmark maintained by Thor Bj. Stadshaug and Lone Katberg Andersen. redirected?
  4. Calendrical Calculations, a useful book by Nachum Dershowitz and Edward M. Reingold.
  5. DAYS and DAGE by Otto Thygesen. DAYS is a nice FREE program designed to assist genealogists in finding dates of named days and generally navigate in and between the Julian and Gregorian calendars. DAGE is the Danish version.
  6. 500 Year Gregorian Calendar (Out of Order) by Stephen Miknenas. A nice online "Date a Day" program using Macromedia's shockwave-flash plugin. NEW URL (2003.03.13)
  7. Handy webinterface to cal by Max Zomborszki. An online Gregorian calendar from where you can make a useful print of all days and months in a whole year. NEW URL (2003.03.13)


If you have any suggestions for improvements, please let me know:
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Updated on 2015.09.07