The Perpetual Calendar

A helpful Tool to Postal Historians

By Toke Nørby

Updates and Acknowledgements


A Perpetual Motion Wheel!

Updates to

I here mention important changes since 17 November 1995 (1995.11.17) in the "Calendar" so you can make changes in your printout or take a new one.

  1. 2014.03.25. John Harper, New Zealand, suggested that I mention the special story about Hawaii. John has been so kind pointing me to the special fact that Hawaii never used the Julian calender.
  1. 2008.11.08. First of all I lost a good e-mail friend, Lance Latham, who passed away on 2008.08.12.
        Thanks to Alexandre Galinos, Greece, I have added some informations to the calendar changes in Greece, Albania, Bulgaria and Serbia. Thanks also to Andreas Birken, Germany, who has corrected the text in the section "What about Turkey" and who also added a note about the use of the Gregorian calendar by the Turkish post.
  1. 2002.10.31. Marc Thioux has found that the years 1593-1600 on my page were wrongly placed in the Scheme 2 (column two). Marc Thioux was undertaking the experimental investigation of a young adult with an autistic syndrome who is able to compute the weekday corresponding to a given date very quickly. He was trying to check the responses of this patient with my perpetual calendar based on the reform of 1582 and found the error which unfortunately has been there since the page was uploaded first time on 2000.02.29.
  1. 2000.02.29. In this "300th anniversary" version I have actually made several changes and additions. In Scheme 1.1-1.3 I have listed information on the Calendar Reform where older territories are placed under the modern states they belong to nowadays, thanks to Manfred Kiefer, Germany. I have corrected a few wrong dates:
        Bulgaria: Last Julian date "1915.11.01" corrected to "1915.10.31". Germany, Pfals-Neuburg: First Gregorian Date: "1615.12.14" corrected to "1615.12.24". Yugoslavia: Last Julian date "1919.01.17" corrected to "1919.01.14". First Gregorian Date: "1919.01.31" corrected to "1919.01.28". Thanks to Branislav Skrobonja, Yugoslavia.
        I have added new information to Israel, thanks to Amos Shapir, Israel; to Romania, thanks to Dan Grecu, Romania; and to Yugoslavia, thanks again to Branislav Skrobonja, Yugoslavia. I have also added a little news to the sections describing Turkey and Denmark.

    I have reorganized Scheme 2 and 3 as I would like to indicate that the first Day of the week (DOW) is a Monday as it is in Denmark. Furthermore I have indicated that the exact cycles in the Gregorian Calendar are 400 years where the so-called year types are repeated. This means that you now can jump to a date as far in the future as you want. I have also - and just to please you (did I? :-) made a separate page with perpetual calendar using Pope Gregor XIII's change over dates in october 1582. You will find that calendar after the section: "The Gregerian Tip"!

  1. 1999.11.05. In this version 1999.11.05 I have only added the story of the Danish change over. Reference (w1) has moved: Calendar FAQ by Claus Tøndering. Plus, as usual, made a few minor corrections in the text.
  1. 1999.01.11. Additional information on Calendar reforms back to October 1582 are added in my Schemes 1.1-1.3 - including references to my sources, thanks to Manfred Kiefer and Lance Latham (2008.08.12). The Netherlands and Yugoslavia (Scheme 1.3) are added, thanks to Willy Ahlers, The Netherlands - see the literature reference (5), and Dik Winter, reference (e9).
        I have also included new information on Russia thanks to Maxim V. Kollegov (Aka "Virtual_Max" - Reference 16) and his friend Andrej Shapovalov who is the director at the Novosibirsk Museum. First, my year for the year of adopting the Julian calendar in Russia was wrong as 1709 was the year when the first Gregorian calendar was printed in Russia, and Andrej Shapovalov told me (via Maxim) that Russia according to a law dated in the year 7208 (Byzantine Calendar with New Year on 1 September) announced that Russia adopted the Julian Calendar from 1 January 1700 JU. Furthermore Andrej Shapovalov told Maxim that the decreed that introduced the Gregorian calendar from 1 February 1918 GR was signed on 26 January 1918 JU. Andrej Shapovalov also found unknown - at least to me - dates for the calendar change in Russia and told me that the laws of the Kolchak's government which was published on 1918.10.31 JU in Omsk city included a law about the calendar change under his government: The Last Julian date was 1918.09.30 JU and the first Gregorian date was the following day, 1918.10.14 GR.
        Maxim V. Kollegov has kindly allowed me to use his JAVA applet VMaxCalendar on my site and I have inserted the calendar reform dates in various countries according to my schemes 1.1-1.3.
        The URL and e-mail The International ISO 8601 Format Dates by Markus Kuhn changed on 1998.09.17. (See r7 ???). Finally, I have made some minor corrections in the text.
  1. 1998.01.05. Thanks to Simon Cassidy who told me about a couple of references which caused me to change the text in the second paragraph in the section with the headline The Julian Calendar (according to the new reference (w2) - the old reference was incorrect) and in my paragraph What about England? where I had the wrong statement that Scotland switched from the Julian to the Gregorian calendar in 1600. According to the new reference (w4) - which also has been changed in this update - this happened at the same time as in England, so, Scotland is now included in Scheme 1.2.
        In the section "What about Russia?" I now show a postcard sent from Denmark to Russia and postmarked in both Gregorian time (Denmark) and Julian time (Russia). Finally, I have added a new reference for the time in Scotland, see reference (9), thanks to Angela Lamb, and made a few minor corrections in the text.
  1. 1997.11.28. In this version I have added a few links at the end of the document: a link to SCDTL (The Standard C Date/Time Library) by Lance Latham (), a link to a very useful Universal Calendar Calculator by Ira Johan Lund and a link to a site with a list of free- and shareware calendar programs/interactive, perpetual and web calendars. Finally, I have made a few minor corrections in the text.
  1. 1997.10.20. Thanks to John Rickard, who drew my attention to a WWW page with the original text of the Act for Regulating the Commencement of the Year; and for Correcting the Calendar now in use by Mark Brader. According to this reference (7) I have now corrected the text in the paragraph "What about England?". The former text in the mentioned paragraph was unfortunately based on a WWW reference with incorrect information.
  1. 1997.07.04. Scheme 1.2 and the text in the "Russian Section" have been changed. Thanks to Inge Marie Larsen who drew my attention to "Labor in The Soviet Union" by Solomon M. Schwarz. Praeger, New York 1951 (15), and Boris Weil, Copenhagen, Denmark, who explained the special situation in Russia in the period between 1923-1940 and that the Gregorian Calendar was in use from its introduction in 1918.
  1. 1997.01.31. Thanks to Paul A. Barkley who drew my attention to two bad URL's: Reference (w1) Calendar FAQ by Claus Tøndering) had moved and Reference (w3) "Genealogy, Calendars and Dating" by James P. Terry had 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!).
  1. 1996.11.07. First, additional information on Calendar changes in The Netherlands and Yugoslavia (Scheme 1.2) are added, thanks to Willy Ahlers, The Netherlands - see the literature reference (5). Second, P.H. Honig told me that the Greek Embassey 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 (Added to Scheme 1.1). Finally, I have made some minor corrections in the text.
  1. 1996.09.10. As you see, dates are now written in (nearly) ISO 8601 date format - suggested by Paul Eggert and Lawrence A Crowl, both USA. (See eventually A Summary of the International Standard Date and Time Notation by Markus.Kuhn). The correct ISO 8601 date format is 1996-09-10 but as I often use hyphen to separate dates in a period (e.g. 1996.01.01-1996.02.01), I decided to use "." instead of "-". In this version I have made many, many minor corrections (Scheme 2 and 3 are still both correct!). Scheme 1.1 and 1.2 has been revised. New information (from other WWW-pages) has been included - all mentioned with reference. Scheme 6 has been corrected: for the period "1712.01.01-1712.02.30 use 1644" (1633 was wrong) and for the period "1712.03.01-1712.12.31 use 1651" (1645 was wrong). Finally, more calendar relevant references are included in my article.
  1. 1996.02.07. New information on The French Republican Calendar: English names for the Republican months and information on the period where this Calendar were in use. (Thanks to Bob de Violini, USA).
  1. 1996.02.03. Two "fatal" errors are found in Scheme 2: First, the reference line for 1900: "00" is misplaced. In the 1801-1900 column the line "16 44 72 00" is corrected to "16 44 72" and the line "21 49 77" is corrected to "21 49 77 00". Second, the reference for the year 2000 is missing. It should read "00" directly under the "99" in the 1901-2000 column: the line "16 44 72" is corrected to "16 44 72 00". Sorry for this misinformation - although the scheme is correct in my book (2) in the mentioned reference list in "The Perpetual Calendar". (Thanks to Kevin Harbol, USA).
  1. 1996.01.29. In Scheme 1: Iceland inserted (thanks to Ólafur Elíasson, Iceland) and Scheme 1 is simplified.
  1. 1995.12.24. In Scheme 6: "01.02.1712" corrected to "01.03.1712".
  1. 1995.11.17. The Perpetual Calendar was released first time.


Back to "The Perpetual Calendar"
Back to Toke Nørby's home page
All links are checked on 2002.12.01