The recent significant progress on both the theoretical and observational researches on white dwarfs promotes the application and development of white dwarf cosmochronology. The idea of such a chronometry is to calculate the theoretical luminosity function using white dwarf cooling tracks and compare it with observational luminosity function to constrain the ages of various populations of evolved stars in the Galaxy accordingly. In this review, we first briefly describe the basic properties of white dwarfs, and then review the history and basic methods of white dwarf evolution researches. We also describe the basic principle of white dwarf cosmochronology and its application in defining the age of the Galactic disk, globular clusters, open clusters and Galactic halo. Although white dwarf cosmochronology is still in its infancy, it already shows its potential as a powerful tool for estimating the ages of the various objects. Finally we discuss the uncertainties existed in current research and suggest some further investigations on it.