Polish flag day is May 2 . There was also a historical reason : under the Communist regime , May 2 was a day when national flags , hoisted for Labor Day on May 1 were being quickly removed before Polish Constitution Day ( May 3 ) , which was banned by the authorities . Since the re-introduction of the Constitution Day in 1990 and establishment of the Polish Flag Day , the flag is flown continuously during the first three days of May .