As the years went on, time due to the miscalculation in the previous Julian calendar accumulated. This meant countries who adopted it later had to make a change of more days. When Britain (and the American colonies) adopted the calendar in 1752, it was necessary to add 11 days. In Russia, the change was not implemented until 1918. At that point, a shift of 13 days was required to correct the discrepancy.
Today is also the Epiphany; here in Poland the day is colloquially known as “Święto Trzech Króli” or “Feast of the Three Kings” (or just “Trzech Króli” for short).
You can read more about the history of the day, and Amish observance here: Amish Old Christmas.
Photo credit: JimGoings-Studiographics/flickr