Age appropriateness refers to people behaving as predicted by their perspective timetable of development. The perspective timetable is embedded throughout people's social life, primarily based on socially-agreed age expectations and age norms. For a given behavior, such as crawling, learning to walk, learning to talk, etc., there are years within which the behavior is regarded appropriate. By contrast, if the behavior falls out of the age range, it will be considered age-inappropriate. Most people are adhered to these age norms and are aware of whether their timing is "early," "delayed," or "on time."