A method for recording a duration of use of a data block is disclosed, as well as a data storage device implementing that method. The data block is either an in-use data block or an empty data block. The method includes steps of: receiving and writing data into one of the in-use data blocks and writing a program time and a time interval of the data into the in-use data block. Wherein the time interval is a difference between the program time and an initial program time of the in-use data block, and the initial program time was recorded when the in-use data block wrote a first piece of data.