Method of scheduling jobs in storage device using pre-defined time and method of operating storage system including the same

In a method of scheduling jobs in a storage device, a first job is performed. While the first job is being performed, a first timestamp for the first job is pre-updated based on a pre-defined operation time table that represents a relationship between operations of the storage device and operation times. While the first job is being performed, scheduling requests are received that are associated with a second job to be performed after the first job. While the first job is being performed, a scheduling operation for selecting the second job is pre-performed based on the scheduling requests and the timestamps.