A clock determination method executed by a first one of apparatuses included in a system includes receiving a list including first definite clock values of respective apparatuses, the list being circulated among the apparatuses; determining the first clock value of the first apparatus at a point in time based on a smallest of logical clock values regarding corresponding commands on which processing is not completed, the commands being included in commands received by the first apparatus and the logical clock values being obtained at a time of receiving the corresponding commands and being stored, and updating the first clock value, the updated first clock value being included in the list, by using the determined first clock value; specifying, as a second clock value for the system, a smallest of the first clock values included in the updated list; and transmitting the updated list to a second one of the apparatuses.