Why Do Many Records List Two Dates?

Birth, marriage, and death records in Russian-ruled Poland from about 1867 to 1915 list two dates, informally called old style and new style.

The old style followed the Julian calendar and was used officially in the Russian Empire. The new style date followed the Gregorian calendar and was used by Poles as well as most of Europe.

During most of the 1800s, there was a 12-day gap between the two calendars. Therefore, the two dates displayed for events in most of the 1800s differ by 12 days. Here is an example: 7 / 19 May 1869 means 7 May in the Julian (old-style) calendar and 19 May in the Gregorian (new-style) calendar. In 1900, the gap increased to 13 days.

Understanding why two dates were listed — and why this practice occurred from the mid-1860s to the mid-1910s — requires some knowledge of Polish history:

“In 1772, Austria, Prussia, and Russia took advantage of Poland’s weakness and partitioned…Polish territory among themselves. Austria seized land in southern Poland. Prussia took land located in western Poland. Russia took land in the east. … In 1830, Poles in the Kingdom of Poland rebelled against the Russians. But Russia crushed the revolt. Other unsuccessful revolts were launched against Austria and Prussia. After a second revolt in the Kingdom of Poland in 1863, Russia tried to destroy Polish culture by making Russian the official language there. … After the outbreak of World War I in 1914, [Józef] Piłsudski led Polish forces on the side of Austria against Russia. The Russians were driven out of most of Poland by 1915.”

Source: Janusz Bugajski, Director, New European Democracies Project and Senior Fellow, Europe Program, Center for Strategic and International Studies, Washington, D.C., in “Poland,” World Book Advanced, 2024.

Here is more information regarding the Julian and Gregorian calendars.

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