Police use water cannons on May Day demonstrators in Istanbul, Turkey, on Friday, May 1. Clashes erupted between police and protesters, who defied a government ban  on marching to Taksim Square. Rallies around the world marked &lt;a href=&quot;http://www.cnn.com/2013/09/03/world/may-day-fast-facts/index.html&quot;&gt;May Day&lt;/a&gt;, referred to as International Workers' Day in many countries.