1. A shared experience information construction system comprising: an information terminal device of a first user; an information terminal device of a second user; and a server device connected to the information terminal devices of the first user and the second user via a network, wherein the information terminal device of the first user includes a content selection unit that selects a content on a prescribed experience by the first user, a content identification information output unit that outputs information that identifies the content selected by the content selection unit to the information terminal device of the second user, a first unique key generation unit that generates a unique key corresponding to the content selected by the content selection unit, and a first user information transmission unit that transmits information on the first user, a unique key generated by the first unique key generation unit, and information on the content to the server device via the network, wherein the information terminal device of the second user includes a content identification information input unit that inputs the information that identifies the content output from the information terminal device of the first user, a second unique key generation unit that generates a unique key corresponding to the information that identifies the content input by the content identification information input unit, and a second user information transmission unit that transmits information on the second user, the unique key generated by the second unique key generation unit, and information on an input date and time and/or an input location of the information that identifies the content input by the content identification information input unit to the server device via the network, wherein the server device includes a unique key collation unit that collates the unique keys transmitted from the information terminal device of the first user and the information terminal device of the second user, a shared experience information construction unit that defines the input date and the time and/or the input location of information that identifies the content transmitted from the second information terminal device as a shared date and time and/or a shared location of the content when a collation of the unique keys has been successfully performed by the unique key collation unit and correlates the information on the first user, the information of the second user, the information on the content, and the information on the shared date and time and/or the shared location with each other to construct shared experience information between the first user and the second user, and a shared experience information storage unit that stores the shared experience information between the first user and the second user constructed by the shared experience information construction unit.