It's Children's Day!

In what countries do people celebrate this day? When is Universal Children's Day?

Read in Wikipedia
Children's Day in Russia

Права детей (10 мультфильмов на английском языке)
10 Top Cartoons on Children's Rights both for children and adults
All children have the rights to health, to education, to an adequate standard of living, to leisure and play, to protection from exploitation, to express their own opinions … and many more.