Posted by Esther Yu Sumner on January 19, 2016 in Research

This post originally appeared in Ancestry Magazine, March-April 2007 issue.  bigstock-Calendar-5486981-300x200

What, you say, that can’t be right. Ancestors’ birthdays don’t just change, do they?

They might, if you’re looking at the wrong calendar.

Most of us are familiar with a single calendar—the Gregorian calendar, the one we use today. But, depending on the country, not all that long ago, your loved ones might have been living with the Julian calendar.

Setting a Date

Just like our current Gregorian calendar, the Julian calendar was based on the vernal (spring) equinox. But the Julian calendar listed March as the first month of the year. Leap years were employed to help keep months aligned with the seasons, but one leap year every four years wasn’t sufficiently accurate.

The Gregorian calendar, on the other hand, ensured that dates would be more accurately aligned with seasons. The Gregorian calendar also fine-tuned the leap year idea by removing three leap years out of every 400 years and by switching the first day of the year to 1 January rather than 25 March.

Confusing? Well the good thing is that calendar changes probably won’t affect you today—unless you’re a family historian. That’s when all of those date discrepancies and shifting numbers add up to a lot of confusion.

Consider this. An individual country may have adopted the Gregorian calendar any time between 1582 and the early 1900s. During the year the calendar was adopted, the country would have dropped 10 or 11 days from the year. But just like not every country adopted the Gregorian calendar at the same time, neither did any single country’s residents. And how those 10 or 11 days were dropped was completely up to the country making the change.

Take, for example, the calendar change that occurred on 4 October 1582, when Spain, Portugal, and Italy skipped 10 days, and each bumped their calendars to 15 October 1582. While 12 October 1582 did not technically exist in those countries, finding a document with that date while researching isn’t necessarily inaccurate—it could just mean that document was created by someone who waited a month or so to adopt the change.

So an ancestor’s birth date reading 5 October 1582 in one record and 16 October 1582 in another record may not signal a recording error. And double dates, recorded with slashes such as 15 March 1700/01, aren’t old-school typos—they’re used to show both Julian and Gregorian calendars.

Muddling Through

One of the greatest challenges a family historian finds when facing date changes is knowing—and understanding—when each ancestor’s country changed to the Gregorian calendar. The British colonies, including North America, didn’t move to the Gregorian calendar until 31 December 1751, which was then followed by 1 January 1752 (the Julian calendar would have read 1 January 1751—the year would have changed in March). The 11 days of inaccuracy from the Julian calendar were accounted for by omitting 2–14 September 1752. Alaska, which belonged to Russia when North American colonies made their switch, didn’t change to the Gregorian calendar until 1867.

Canada switched to the Gregorian calendar on 2 September 1752 and skipped immediately to 14 September 1752. France made the switch on 9 December 1582. The Catholic regions of Germany made the switch in various months of 1583 while most Protestant regions made the switch between 1615 and 1668. China never used the Julian calendar but started using the Gregorian calendar in 1912.

Adding Confusion

Quaker dates can be especially confusing since Quakers typically dated by number and because there was no official day on which every Quaker switched calendars.

“Before 1752, Quakers were using both calendars at the same time,” says family historian William Dollarhide. Using a number system, you may come across a date like 2/10/1720—on the Julian calendar, that date would be 10 April 1720; Gregorian, it would be 10 February 1720.

“I have come across a case where the only way I could tell if they were using a Julian or Gregorian calendar was to look through every other date in the record book to find some other numbers and see if those were Gregorian or Julian,” says Dollarhide. “It was a revealing experience to understand that for Quakers in particular you have to really watch the dates.”

Quaker dates may not be the only problematic ones you come across. But you can still get through calendar changes without too many problems, especially if you keep a couple of things in mind—how and when the country you’re looking at addressed calendar changes; and that a date, while perplexing, is still just a date.

Country              End Julian Calendar   Begin Gregorian Calendar

Albania                          Dec 1912                 Dec 1912


Tyrol                                Oct 5, 1583             Oct 16, 1583

Carinthia, Styria           Dec 14, 1583           Dec 25, 1583


Spanish Provinces       Dec 21, 1582           Jan 1, 1583

Liège                               Feb 10, 1583           Feb 21, 1583


(Czech Republic)            Jan 6, 1584            Jan 17, 1584

Bulgaria                            Nov 1, 1915             Nov 14, 1915

China                                                                  Jan 1, 1912

Canada                               Sep 2, 1752            Sep 14, 1752

Denmark                           Feb 18, 1700          Mar 1, 1700

Færø Islands                    Nov 16, 1700          Nov 28, 1700

Egypt                                    1875                         1875

Estonia                              Feb 1, 1819            Feb 15, 1819

Finland                             Feb 17, 1753           Mar 1, 1753

France                              Dec 9, 1582            Dec 20, 1582

Alsace                               1648                         1648

Strasbourg                      Feb 5, 1682             Feb 16, 1682

Germany –

Catholic Regions

Augsburg                        Feb 13, 1583          Feb 24, 1583

Baden                               Nov 16, 1583         Nov 27, 1583

Bavaria                            Oct 5, 1583            Nov 16, 1583

Cologne                            Nov 3, 1583          Nov 14, 1583

Jülich                                Nov 2, 1583          Nov 13, 1583

Mainz                               Nov 11, 1583         Nov 22, 1583

Münster, Strasbourg    Nov 16, 1583         Nov 27, 1583

Trier                                 Oct 4, 1583            Oct 15, 1583

Würzburg                       Nov 4, 1583          Nov 15, 1583


Protestant Regions

Hildesheim                     Mar 15, 1631         Mar 26, 1631

Kurland                           1617                        1617

Minden                            Feb 1, 1668            Feb 12, 1668

Neuburg                          Dec 13, 1615           Dec 24, 1615

Osnabrück                      1624                         1624

Paderborn                      Jun 16, 1585             Jul 27, 1585

Prussia                            Aug 22, 1610             Sep 2, 1610

Westphalia                      Jul 1, 1584                Jul 12, 1584

Germany, All Others        Feb 18, 1700          Mar 1, 1700

Great Britain                     Sep 2, 1752            Sep 14, 1752

& American colonies

Greece                                  Sep 14, 1916          Sep 28, 1916

Holy Roman Empire        Jan 6, 1584           Jan 17, 1584

Hungary                              Oct 21, 1587          Nov 1, 1587

Transylvania                  Dec 14, 1590             Dec 25, 1590

Iceland                                 Nov 16, 1700         Nov 28, 1700

Italy                                      Oct 4, 1582            Oct 15, 1582

Japan                                    1873                         1873

Latvia                                   Feb 1, 1918           Feb 15, 1918

Lithuania                            Feb 1, 1918           Feb 15, 1819


(Czech Republic)          Jan 6, 1584            Jan 17, 1584

The Netherlands

Holland, N. Brabant      Dec 21, 1582          Jan 1, 1583

Gelderland, Zutphen    Jun 30, 1700          Jul 7, 1700

Utrecht, Overijssel       Nov 30, 1700          Dec 12, 1700

Friesland, Groningen  Dec 31, 1700            Jan 12, 1701

Drente                              Apr 30, 1701           May 12, 1701

Norway                               Feb 18, 1700         Mar 1, 1700

Poland                                  Oct 4, 1582           Oct 15, 1582

Silesia                               Jan 12, 1584           Jan 23, 1584

Portugal                             Oct 4, 1582            Oct 15, 1582

Romania                            Mar 31, 1919         Apr 14, 1919

Transylvania                   Dec 14, 1590           Dec 25, 1590

Russia                               Jan 31, 1918            Feb 14, 1918

Spain                                Oct 4, 1582             Oct 15, 1582

American Colonies       1584                          1584

Sweden                            Feb 17, 1753           Mar 1, 1753


Lucern, Uri, Schwyz,   Jan 11, 1584           Jan 22, 1584

Zug, Freiburg,


Wallis                              Feb 28, 1655          Mar 11, 1655

Zürich, Bern, Basel,     Dec 31, 1700          Jan 12, 1701

Schaffhouse, Geneva,


Appenzell, Glarus,         1724                          1724

St. Gallen

Turkey                        1927                                 1927

United States

British Colonies       Sep 2, 1752                       Sep 14, 1752

Alaska                        Oct 5, 1867                       Oct 18, 1867

Yugoslavia                Mar 4, 1919                      Mar 18, 1919

Esther Yu Sumner

Esther Yu Sumner loves the genealogy community. She is a former contributing editor of Genealogical Computing, Ancestry magazine, and the Ancestry Daily News. She is also the author of "Military Records at" and "Family Tree Maker 2005."


  1. That chart is slightly misleading for at least one country – Poland.

    Yes – they switched to Gregorian in 1582.

    However, when they came under Russian control in 1815, they reverted back to Julian – until 1918.

    • Juliana Szucs

      Good call out on that exception. And a good reminder to research the history of the area you’re researching thoroughly.

  2. Susan Mowry

    I’m confused. The “American Colonies” adopted the Gregorian in 1584 as well as 1752 but the “United States” adopted it in 1927? Which is correct?

    • Juliana Szucs

      The Spanish colonies in the Americas adopted the Gregorian calendar in 1584. (An indentation that would have made that easier to see got lost in copying the post from the original table format, but I’ve replaced it.) British colonies in America and Canada adopted it in 1752. The 1927 date was an error that I’ve fixed.

  3. Jane Rhoades

    I’m like Susan I’m confused the difference from1584 to 1752 that’s quite a long time and then the United States 1927 which is correct and why the time spand.

  4. Marilynn Dolan

    My mother-in-law was born in 1900 in Siberia and still celebrated her birthday under the Julian calendar. The Russian Orthodox church still celebrates Christmas as January 7, which is the Julian calendar date. Their Easter is more closely tied to Passover than the Roman church.

  5. J.D.

    The 1584 “American Colonies” are probably the ones that belonged to Spain at the time. (They’re listed just below Spain.) The American Colonies belonging to the British converted in 1752. I can’t find any evidence for the United States date of 1927. Is that an error? Or some technicality…?

    • Juliana Szucs

      Apologies again, the dates came from a table and they didn’t come over cleanly. I’ve removed that 1927 date that should have been with Turkey. I also went in and replaced some indentations that also got lost in translation, and that should make it easier to understand. Thanks for keeping us honest. 🙂

  6. Denise

    Converting between Julian Calendar & Gregorian Calendar in one step go to
    This site will help you to convert in many Countries it is a great resource.
    I knew that my grandfather that came from Yugoslavia had one birthday and in the United States it was a different birthday – I had to convert from Julian to Gregorian Calendar. I’m Serbian Orthodox we celebrate Christmas on January 7th each year (Julian Calendar) and this year 2016 Easter will be on May 1st (Julian Calendar). I’m very proud of my heritage and Serbian traditions. I just wish that records can be found in the former Yugoslavia.

  7. rhonda

    Why doesn’t ancestry accept the format for entering the double dates? When I use a slash (Jan 1642/43) it doesn’t show the date in the index when for searching other family trees. Also, I’ve noticed that a lot of the Massachusetts vital records have the wrong date in the index compared to what’s in the actual record. Several times I’ll find a record from the time period of the Julian calendar that lists say the 3rd month, but the ancestry index gives the month as March rather than May. My old family tree maker software automatically converts a date to a double date if necessary – why doesn’t ancestry do that?

    • Juliana Szucs

      When you start adding slashes and other non-standard symbols, it can cause some issues with the way dates are displayed so facts may appear out of order. I would use the date that is on the record and use the description for that fact or the notes/comments to add the additional date information.

  8. June Kiger

    My father was born in Latvia. I noticed that the year 1918 was 1819. This is a very large span in years. Is this a “typo” ? Thank you

  9. calyx

    In certain parts of the U.S. birth certificates were not required until after WWII. If registered, the records are mostly for sons, not daughters. Additionally, due to racist practices in this country, people did not want their multiracial children labeled as “black”. Beyond that, some times the pittance cost of the registration was too much for poor people. That’s why the certificate was a year or three after the child’s birth.

  10. Michael.myshka

    The new program dies not show my notes or exsirps from different historic books from national archives from America, UK, Germany and Poland now. I had them written as footnotes with book title, copyright, authors, and pades listed.

  11. Denise

    I also noticed that the date on Lithuania Feb 1, 1918 Feb 15, 1819
    The last date Feb 15, 1819 needs to be changed to the correct date. Thanks

Comments are closed.