A first wireless communication device comprising: a storage unit configured to store identification information of a second mobile device; a communication unit configured to receive time zone information of the second mobile device ; and a processor configured to: compare time zone information of the wireless communication device with the time zone information of the second mobile device , control a display unit of the first wireless communication device to display the time zone information of the second mobile device on a message transmission reservation setting window for setting a message transmission reservation time, in response to the time zone information of the first wireless communication device being different from the time zone information of the second mobile device , control a user input unit of the first wireless communication device to receive a user input relating to setting the message transmission reservation time based on the time zone information of the second mobile device , and control the communication unit to transmit a reserved message to the second mobile device when a time of the second mobile device reaches the message transmission reservation time. a storage unit configured to store identification information of a second mobile device; a communication unit configured to receive time zone information of the second mobile device ; and a processor configured to: compare time zone information of the wireless communication device with the time zone information of the second mobile device , control a display unit of the first wireless communication device to display the time zone information of the second mobile device on a message transmission reservation setting window for setting a message transmission reservation time, in response to the time zone information of the first wireless communication device being different from the time zone information of the second mobile device , control a user input unit of the first wireless communication device to receive a user input relating to setting the message transmission reservation time based on the time zone information of the second mobile device , and control the communication unit to transmit a reserved message to the second mobile device when a time of the second mobile device reaches the message transmission reservation time. compare time zone information of the wireless communication device with the time zone information of the second mobile device , control a display unit of the first wireless communication device to display the time zone information of the second mobile device on a message transmission reservation setting window for setting a message transmission reservation time, in response to the time zone information of the first wireless communication device being different from the time zone information of the second mobile device , control a user input unit of the first wireless communication device to receive a user input relating to setting the message transmission reservation time based on the time zone information of the second mobile device , and control the communication unit to transmit a reserved message to the second mobile device when a time of the second mobile device reaches the message transmission reservation time. <EOS>