While these tweets mainly focus on kids making adults feel older than they are, some people do suffer from the opposite problem of living with so-called babyfaces. In their case, their looks just don't catch up to their age. Of course, this is subjective–they won't be asked for I.D. in every bar. These people are in the company of celebrities like Leonardo DiCaprio, with several childlike facial features, such as short nose and plump cheeks. Those features are called neotenous. Scientists are investigating the relationships between neoteny and perceived attraction in different sexes.
Speaking of relativity and years, there is a well-known phenomenon that people feel time flowing faster as they age. One of the hypotheses is that shorter and more reliably working paths between neurons allow young people to process more information during the same time frame, leaving them with the impression that more things have happened, therefore more time has passed. (Kind of like watching a modern movie with 24 frames per second versus an early with 16-18 fps.) Imagine watching the melodrama Santa Barbara for 9 years and thinking that each episode was shorter than the last. However, this is just one of the hypotheses–there is no consensus yet.
There are several scientific studies on kids' comprehension of age, such as "Now I’m 3: Young Children’s Concepts of Age, Aging, and Birthdays," which you can read in full here. One of the focuses of the study is Western children's ability to understand the relationship between having a birthday party and actual aging (Western, because birthdays are treated with great importance here).
Different cultures not only have different birthday celebration traditions, but age calculating systems as well. In Korea, your age would be different—it would not matter what day you were born, you would be the same Korean age all year. You can calculate it here.
Understandably, senescence is a hard thing for adults to cope with: the feeling of having not achieved enough, losing smoothness in skin and motion. Some works of fiction play on this fear of aging by exaggerating how fast it happens, such as Hayao Miyazaki's Howl's Moving Castle from 2004, or M. Night Shyamalan's 2021 film Old. However, there are real-life conditions causing premature aging. Hutchinson-Gilford progeria syndrome, sometimes nicknamed Benjamin Button disease, is one of them. Hopefully, medicine will soon be able to help people who have it more effectively.
