Prima Aprilis - Polish tradition and the 1683 treaty backdating

APR 01 1683

Poland's April Fools' tradition is called Prima Aprilis, most likely arriving via Germany and France. Its seriousness is documented by a striking episode: the Polish anti-Turkish alliance with Leopold I, signed on 1 April 1683, was backdated to 31 March out of concern that a treaty signed on that date might be dismissed as a joke. A recurring annual custom; earlier Polish attestation claims (13th century) are not firmly documented.