Dyngus Day is observed on April 17, 2017. ?migus-Dyngus, also known as lany poniedzia?ek, meaning "Wet Monday", is a celebration held on Easter Monday in Poland. It is also observed by Polish diaspora communities, particularly among Polish Americans, who call it Dyngus Day.
Traditionally, boys throw water over girls and spank them with pussy willow branches on Easter Monday, and girls do the same to boys on Easter Tuesday. This is accompanied by a number of other rituals, such as making verse declarations and holding door-to-door processions, in some regions involving boys dressed as bears. (With material from: Wikipedia)