Are You Using the Right Calendar?

Are you researching an historical event in two separate countries and finding that the dates don’t match?  Do you have documents that list a different birth, marriage or death date for an ancestor?  Are you wondering which date is correct?  Well, just maybe they both are.

Not all countries or ethnic groups use the same calendars.  Nor have all calendars held constant through time.  If you have two official documents with two different dates for the same event, see if you can determine which calendar was used for each of those documents.

Today, I’m only going to provide a brief introduction to two such calendars in use today, the Julian calendar and the Gregorian calendar.  Both initially come to us from Rome.  Both were named after the leader that proposed or introduced the new calendar, rather than the persons that developed the calendars.

 

Julian Calendar

The Julian calendar, proposed by Julius Caesar, took effect January 1, 45 B.C., replacing the former Roman calendar.  Most of Europe and persons in European settlements and colonies used the Julian calendar for several centuries.  The Berbers still use it today. It is also in use in areas of the world where the Eastern Orthodox Church and Oriental Orthodoxy have a strong influence.  

The creators of the original Julian calendar overestimated the length of a solar year by 11 minutes and a few seconds.  That doesn’t seem like much; but over time that little bit adds up.  Even with the adjustment of leap years, by the 1500s, Easter, which was traditionally celebrated on March 21^st, no longer lined up with the spring equinox. 

 

Gregorian Calendar

Pope Gregory XIII commissioned a new calendar to bring Easter back in line with the spring equinox and to reduce the error in measurement. The Gregorian calendar was introduced via a papal bull in Oct 1582.  However, even with the new calculations, 10 days still needed to be removed from the calendar to bring Easter back in line with the spring equinox. Therefore, in 1852, October 4th was followed by October 15th.  Can you imagine losing 10 days overnight?

The Pope has no official authority outside of the Catholic Church; so actual adoption of the Gregorian calendar took place at different times in different countries. The first countries to adopt the Gregorian calendar were predominately Catholic. Italy, Poland, Portugal, Spain and parts of France adopted the Gregorian calendar in 1582.  German Catholic principalities and states followed suit in 1583.  It would be 1700 before German and Swiss Protestant states and principalities would adopt the Gregorian calendar.

 

Understanding the Difference Between Calendar Dates

As time moves forward, the two calendars move further apart. As a result, the number of days adjusted between the two calendars varies. 

For example:

• when the United Kingdom and its colonies adopted the Gregorian calendar in 1752, eleven days were removed from the calendar. 
• By the time Russia and Estonia adopted the Gregorian calendar in 1918, thirteen days had to be removed from the calendar.

Officials in each state, principality and country determined when those days would be removed from the calendar.

While most of us are used to the calendar year starting on Jan 1, it has not always done so.  In England, for example, prior to the adoption of the Gregorian calendar, the legal New Year began on March 25^th.  So when England and her colonies adopted the Gregorian calendar, not only did the date change, adjustments were made to the year as well! 

While the Gregorian calendar was more accurate than the Julian calendar it replaced, it was still 27 seconds too long.  In 1923, a Serbian revised the old Julian calendar.  While the revised Julian calendar is more accurate than the Gregorian calendar, it is only used in limited places.

So, if you are looking at two different documents/sources which have recorded the same event on different days, check to see which calendar was in effect, and verify the adjustment needed to bring the calendars into alignment.

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