Century eggs aren’t eggs that were preserved for a century. The process only takes a few weeks to months. Century egg originated in China but it can easily be found in other Asian countries, especially in Chinese restaurants.
The process involves putting duck, chicken, or quail eggs in a saline solution which has clay, salt, rice hulls, quicklime, and even ash. Because of the unique process, the eggs turn creamy and resemble the texture of cheese. It also changes color from white to a jelly-like dark color.