6. The non-transitory computer readable medium of claim 3 , wherein the keyword extraction unit is operable to extract keyword appearance times for the extracted keyword from a content appearance time.
6. The non-transitory computer readable medium of claim 3 , wherein the keyword extraction unit is operable to extract keyword appearance times for the extracted keyword from a content appearance time. 8. The non-transitory computer readable medium of claim 6 , wherein the time pattern extraction unit is operable to obtain a time interval from a current time to the keyword appearance time and a time interval between the keyword appearance times, and to obtain the first time pattern from the time intervals using a statistical probability distribution function.