The holiday date was chosen for two reasons. On 2 May 1945, the First Polish Army put a flag on the Berlin Victory Column and the Reichstag in Berlin. The second is that the communist authorities abolished the celebration of the 3 Maj Constitution Day and the flags had to be removed.
“The holiday was set in the form of other countries, especially the United States, where it was first established to commemorate the adoption of the first American flag of 1777,” explained Andrzej Bełowski in 2018.
Although the Polish flag is made up of two horizontal bands – white and red – it is no longer easy to specify the shades of these colours. "The Act of 31 January 1980 on the emblem, colours and anthem of the Republic of Poland and State stamps" reveals that colours are presented in the form of trichromatic coordinates. This means that the white is not a pure snow-white, and the red colour is crimson or a dark red.
National colours are also of symbolic importance. As Andrzej Bebłowski pointed out, "white colour symbolizes gentleness, friendship, prosperity and red colour blood, i.e., the struggle for sovereignty, the fight for independence". During World War II, the white and red colours were also a symbol of the nation's infirmity and will to win, and they gave hope for freedom.
There are two types of Polish state flag. The first is a white/red rectangle. The second flag with the emblem of the Republic of Poland on the white strip. According to the law in force, flags with emblem can only be used by the official national agencies abroad, by civil airports and aircraft, by port masters as well as by Polish sea ships as a flag.
Source: Poland Daily, niezalezna.pl, pap.pl