Western Christianity celebrates the Feast of the Annunciation (or contemporary Solemnity of the Annunciation) annually on March 25. This feast commemorates the visit of angel Gabriel to the Virgin Mary.
Many countries celebrate International Day of the Unborn Child. It annually falls on March 25.
Tolkien Reading Day is an annual event, devoted to reading the works by J. R. R. Tolkien and use of his works in education and library groups.
March 25 is International Day of Solidarity with Detained and Missing Staff Members, that is annually observed by the UN.
International Day of Remembrance of the Victims of Slavery and the Transatlantic Slave Trade is one of the UN international days, that is annually observed on March 25. This observance was created in 2007 and it's first celebration took place in 2008.