An operating method of a storage device which includes a nonvolatile memory is provided. The operating method includes performing a first program operation on selected memory cells of the nonvolatile memory and storing a first time when the first program operation is performed; and adjusting a program parameter according to a difference between the first time and a second time, and performing a second program operation on the selected memory cells using the adjusted program parameter, the second time being a time when the second program operation is performed.