Ephebophilia
Specific words are used by scientists for chronophilias, which is when people are mostly or only sexually attracted to specific age groups. Along with ephebophilia, another example is hebephilia, which means that a person is mostly or only sexually attracted to younger pubescent people. The word pedophilia means that a person is mostly or only sexually attracted to pre-pubescent children; but the term pedophilia is commonly misused to refer to any sexual interest in minors under the age of 18, even if they're post-pubescent.