Although most countries in Western Europe adopted the Gregorian calendar by the end of the 18th century, Eastern Europe did not convert from the Julian to the Gregorian calendar until early in the 20th century.

SSA assumes the Julian calendar was used and converts the date to the Gregorian calendar date if a document (other than a Roman Catholic record) was issued or recorded in Eastern Europe at the time the Julian calendar was used (see GN 00307.180D.).

SSA does not assume all documents or records made after the dates in GN 00307.180D. used the Gregorian calendar since some registrars continued to use the old calendar.

SSA assumes records issued in countries not listed in GN 00307.180D. show Gregorian dates.

Convert a Julian calendar date to the Gregorian calendar date by adding:

• •

  12 days to dates prior to March 1, 1900; and

• •

  13 days to dates after February 28, 1900.

This chart gives information on the dates the countries listed converted to the Gregorian calendar and the calendar by which dates are shown on subsequent certifications.