【Europe Day - EU Open Doors】

To celebrate Europe Day, the EU institutions open their doors to the public on 2 May in Strasbourg and on 9 May in Brussels and Luxembourg. Local EU offices in Europe and all over the world organise a variety of activities and events for all ages.
Each year thousands of people take part in visits, debates, concerts and other events to mark the day and raise awareness about the EU.

【The European anthem】

The melody used to symbolize the EU comes from the Ninth Symphony composed in 1823 by Ludwig Van Beethoven, when he set music to the "Ode to Joy", Friedrich von Schiller's lyrical verse from 1785.
The anthem symbolises not only the European Union but also Europe in a wider sense. The poem "Ode to Joy" expresses Schiller's idealistic vision of the human race becoming brothers - a vision Beethoven shared.

【The European flag】

The European flag symbolises both the European Union and, more broadly, the identity and unity of Europe.
It features a circle of 12 gold stars on a blue background. They stand for the ideals of unity, solidarity and harmony among the peoples of Europe.

The number of stars has nothing to do with the number of member countries, though the circle is a symbol of unity.

Referece: http://europa.eu/about-eu/basic-information/symbols/index_en.htm