when was pluto demoted

Pluto was demoted from its status as the ninth planet of the solar system and reclassified as a dwarf planet on August 24, 2006. This decision was made by the International Astronomical Union (IAU) after they defined the criteria for what constitutes a planet. Pluto meets the criteria of being spherical and orbiting the Sun but does not meet the requirement of clearing its orbit of other debris and objects. The discovery of the dwarf planet Eris in 2005, which is similar in size to Pluto, contributed to the redefinition and subsequent demotion of Pluto.