Stamps - Source picture: Wikipedia
May 1st. was chosen as date for the International Workers' Day by
socialists and communists to commemorate the Haymarket affair in Chicago
which took place on May 4th. 1886.
Haymarket Affair - Source picture: Wikipedia
The police was trying to disperse a public assembly during a general strike for
the 8-hours workday, when an unknown person threw a bomb to the police.
The police reacted by firing on the workers. This action killed 4 workers.
Nowadays May 1st. is in many countries a public holiday. In Belgium there are
a lot of processions and political speeches made by the socialist movement.