I’ve been thinking recently that you can measure your life in groups of 6, and that your multiple-of-6 birthdays are significant. I don’t have a good term for them but the ages 6, 12, 18, 24, 30, 36 …? are milestones in the sense that you have “matured” from your previous years.
At age 6, you’ve learned all the basics about being a human. You know, walking, eating, talking. At age 12, you’ve mastered being a kid and going to school. At age 18, you’ve mastered being a teenager which is actually quite a feat. When you’re 24, you should have mastered how to live and take on the world on your own (rather than being sheltered by your parents). At 30, you should be well on your way at making a living, married, and contributing to society. Finally at 36, you should be a capable parent and used to taking care of kids.
Obviously, these metrics are more reflective of me than general society but it is almost uncanny how multiples of 6 years line up with these tiers. At age 42, I can take a look to see what the next 6 years will help me master.