230 million years is the time taken by our solar system to rotate around the Milky Way. Dinosaurs just began to roam on the Earth, the last time Earth was in its current position.
The planets in our solar system orbit around the sun. One orbit of the Earth takes one year. Meanwhile, our entire solar system – our sun with its family of planets, moon, asteroid, and comets – orbits the center of the Milky Way galaxy. Our sun and solar system move at about 500,000 miles an hour (800,000 km/hr) in this huge orbit. So in 90 seconds, for example, we all move some 12,500 miles (20,000 km) in orbit around the galaxy's center.
Our Milky Way galaxy is a big place. Even at this blazing speed, it takes the sun approximately 230 million years to complete one journey around the galaxy's center.
This amount of time – the time it takes us to orbit the center of the galaxy – is sometimes called a cosmic year.