A washing machine system comprising a washing machine and a washing machine information server that can communicate with each other through a communications network, wherein the washing machine information server comprises: a time management section configured to keep a clock running to indicate a current time of day; a command generation section configured to generate a command of various settings to be transmitted to the washing machine; a screen information generation section configured to generate screen information used for setting operation of the washing machine; and a communication unit configured to communicate through the communications network, wherein the washing machine comprises: an operation preprogramming control section configured to control an operation preprogramming task of washing; and a communication unit configured to communicate through the communications network, wherein: the screen information generation section is configured to generate information of an operation preprogramming setting screen for specifying and setting a time of preprogrammed operation; and the command generation section is arranged to compare the set time specified according to the information of operation preprogramming setting screen with the current time of the clock in the time management section to obtain a difference from the current time; characterized in that the command generation section is arranged to generate an operation preprogramming command containing information of the difference converted into time information; the operation preprogramming command is transmitted to the washing machine via the communication unit of the washing machine information server and the communication unit of the washing machine; and the operation preprogramming control section of the washing machine is configured to perform the operation preprogramming task based on the time information of the difference from the current time in the operation preprogramming command. a time management section configured to keep a clock running to indicate a current time of day; a command generation section configured to generate a command of various settings to be transmitted to the washing machine; a screen information generation section configured to generate screen information used for setting operation of the washing machine; and a communication unit configured to communicate through the communications network, an operation preprogramming control section configured to control an operation preprogramming task of washing; and a communication unit configured to communicate through the communications network, the screen information generation section is configured to generate information of an operation preprogramming setting screen for specifying and setting a time of preprogrammed operation; and the command generation section is arranged to compare the set time specified according to the information of operation preprogramming setting screen with the current time of the clock in the time management section to obtain a difference from the current time; characterized in that the command generation section is arranged to generate an operation preprogramming command containing information of the difference converted into time information; the operation preprogramming command is transmitted to the washing machine via the communication unit of the washing machine information server and the communication unit of the washing machine; and the operation preprogramming control section of the washing machine is configured to perform the operation preprogramming task based on the time information of the difference from the current time in the operation preprogramming command.