Saint Casimir's Day

Saint Casimir's Day is celebrated on the anniversary of the death of Saint Casimir, the patron saint of Lithuania and Poland, on March 4. On this day the famous Kaziuko mugė is held.
St. Casimir is the patron saint of many Roman Catholic Churches in the United States which were established by Polish or Lithuanian immigrants. While he is considered the patron saint of Lithuania, Casimir--by blood a royal prince of the ruling Jagiellon dynasty of Poland and Lithuania --is more properly a major patron saint of his homeland. St. Stanislaus of Krakow is sometimes cited as Poland's principal patron saint.
St. Casimir's Day in Roman Catholic parishes is marked with a special Mass said in his honor. 
His feast day--March 4--is an optional memorial according to the Liturgical Calendar of the United States Conference of Bishops. It is, however, kept with great reverence in Roman Catholic parishes of ethnic Polish or Lithuanian origin.
Casimir's Day
Casimir