When did dinosaurs go extinct?

The Cretaceous-Paleogene (K-Pg) extinction event occurred about 66 million years ago, ending the 165-million-year reign of non-avian dinosaurs. A 10-kilometer asteroid struck the Yucatán Peninsula, creating the 180-km-wide Chicxulub crater and releasing energy equivalent to 10 billion Hiroshima bombs. The impact launched trillions of tonnes of dust and sulfur into the atmosphere, blocking sunlight for months to years and dropping global temperatures by up to 26°C (an "impact winter"). About 75% of all species went extinct, including all non-avian dinosaurs, marine reptiles, and pterosaurs. However, avian dinosaurs survived and evolved into today's 10,000+ species of birds.