Ice Saints

The Ice Saints is a name given to St. Mamertus (or, in some countries, St. Boniface of Tarsus), St. Pancras, and St. Servatius in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovene and Swiss folklore. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as "the black-thorn winter".

The period from May 12 to May 15 was noted to bring a brief spell of colder weather in many years, including the last nightly frosts of the spring, in the Northern Hemisphere under the Julian Calendar. The introduction of the Gregorian Calendar in 1582 involved skipping 10 days in the calendar, so that the equivalent days from the climatic point of view became May 22–25.

St. Mamertus is not counted amongst the Ice Saints in certain countries (Southern Germany, Austria, Northern Italy, Czech Republic, etc.), whereas St. Boniface of Tarsus belongs to them in other countries (Flanders, Liguria, Czech Republic etc.) as well; St. Boniface's feast day falling on May 14. St. Sophia, nicknamed Cold Sophia (German kalte Sophie) on May 15 can be added in Germany, Alsace (France), Poland, etc.

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