I’ve never really understood the celebration of birthdays. As a little kid with a (perhaps unhealthy) fascination with military history, I was grateful for the excuse to play laser tag. And parties were fun—bad pizza is still better than 90 percent of meals, and who doesn’t like Fudgie the Whale?

From a young age, though, the practice of gift giving confused me. I used to watch “The Lion King” about once a week, and Timon was always saying things like “Let me get this straight. You know her. She knows you. But she wants to eat him. And everyone’s okay with this?”

So I said to my sister: “Let me get this straight. Chris buys me a Breyer horse even though he has no way of knowing that I already have Secretariat, and I buy him Pokémon cards even though I don’t know Mewtwo from Dragonite?”

“Yes.”

“That’s silly.”

“A little. It’s the thought that counts.”

“If it’s the thought that counts, why do people have to buy stuff?”

“They just do. And if they get you sand art, don’t invite them next year.”

I don’t understand the attention, either. “Congratulations!” say my relatives. I never know if this is a foreign thing, or if they’re actually congratulating me on not having died. “I can’t believe how old you’ve gotten!” Really, second cousin once removed? That’s how time works. We live in a chaotic and mysterious universe, but the orbit of the earth around the sun is very predictable.

Three days ago, I turned 21. I would throw in some tropes about milestones and the passage of time and coming of age and all that, but those are thoughts you’ve thunk and themes you wrote papers on in high school English class. I’m now of drinking age (if not of drinking disposition)—old enough to wonder what I did to deserve such a flat, flavorless Manhattan. I can cross the street without holding my mom’s hand, drive a car, and lose money in a casino. And I’m divisible by seven, which I guess is pretty cool.

Historical birthday nonchalance aside, I’d been feeling a little weird about the whole 21 thing for a while. Last week, I called my parents.

“Let me get this straight. I’m supposed to be a grown up for the rest of my life?”

“Yes,” answered my mom. “But remember—while youth is fleeting, immaturity is forever. I’m 56 and I still don’t know what I want to be when I grow up!”

“Then how am I supposed to figure it out?”