Backdated Treaty    (April Fool's Day - 1683)

On April 1, 1683, King John III Sobieski of Poland signed the Treaty of Warsaw with the Holy Roman Emperor Leopold I, agreeing that each should come to the other's aid in the case of an attack by the Turks. The treaty was subsequently backdated to March 31 to avoid the stigma (and perceived bad luck) of being signed on April 1. To this day, many companies avoid making major announcements on April 1, and couples avoid being wed, because of the perceived "jinx" of the day.