World Party Day (P-Day) is celebrated on April 3, according to Calend.ru.   

It is celebrated as a synchronized global mass celebration of a better world and the creation of desirable reality.

The idea of a coordinated synchronized worldwide party appeared as a work of fiction in the book Flight, A Quantum Fiction Novel, by American writer Vanna Bonta. In the ending of this book, published in 1995, all people in the world celebrated at the same time.