International Children's Book Day is an annual event organized by the International Board on Books for Young People (IBBY). It is observed on April 2 to commemorate the birth anniversary of Hans Christian Andersen, a prominent Danish writer best known for his fairy tales.
The first Sunday in April is traditional celebration of Geologist Day. This professional holiday was established in the Soviet Union in 1980, but after its collapse the tradition to celebrate Geologist Day wasn't forgotten. Nowadays it's a professional holiday of geologist in Russia, Ukraine, Belarus Kyrgyzstan and Kazakhstan.
World Autism Awareness Day is a global awareness day observed annually on April 2. It was established by the UN General Assembly in 2007, and the first observance took place in 2008.