That brings back memories of my visit to the remote Scottish island of Foula. The most westerly of the Shetlands, it still officially adheres to the Julian calendar, which is 13 days behind our habitual Gregorian one. These days, the islanders only use the former for Christmas and New Year celebrations, when all 38 of them gather in one house on January 7 and 14 (in lieu of December 25 and January 1).
Source: wiktionary