A read method of a storage device includes performing a first read operation on a nonvolatile memory device based on a time stamp table storing a program time and a time-read level look-up table indicating a read level shift due to a program lapsed time. A determination is made whether to adjust the time-read level look-up table based on a result of the first read operation. As a consequence of determining to adjust the time-read level look-up table, adjusting the time-read level look-up table through a valley search operation and performing a second read operation on the nonvolatile memory device based on the time stamp table and the adjusted time-read level look-up table.