The memory device selects any one of a first memory cell and a second memory cell based on a number of times that the first memory cell is erased, an elapsed time after the first memory cell is erased, a number of times that the second memory cell is erased, and an elapsed time after the second memory cell is erased, and program data in the selected memory cell. The memory device may improve distribution of threshold voltage of memory cells and endurance of the memory cells.