As college students, we have a lot on our minds -- papers, tests, work, etc. -- so it's easy to forget a thing or two here and there.

But last week I actually forgot how old I was, and I know that can't be normal.

Last week I got an e-mail from a friend who was inviting a number of people to his place for a birthday party in a few weeks.

This invitation got me thinking about my own birthday which will be coming up in less than a month (another thing I had obviously forgotten).

But, for the life of me, I couldn't remember how old I was going to be on that day.

I actually had to pull up the calculator on the computer and do the math.

And then it dawned on me -- once you turn 21, you're not really hung up on how old you are anymore.

Remember when you were a little kid?

How old you were was always in the front of your mind.

Even before you were able to count, when you were at the grocery store shopping with mom and a stranger bent over and asked "and how old are you?" you were able to hold up a couple of fingers and say "this many" with pride.

In fact how old you were was such a part of your life at that point that you would begin to count half-years.

It would actually become a point of argument, as if that half-year actually meant anything in the grand scheme of things.

"How dare you say I'm only six, I'll have you know I'm six ... and a half."

Especially through high school, you're constantly aware of your age because there was always some age landmark to go by.

Like when you turn 12 years old -- that means it's only one more year until you're a "teen."

You're turning 16 years old -- it's almost time to get behind the wheel of the family car, and maybe call MTV and become one of the obnoxious people who have their "Sweet Sixteen" party filmed.

Turning 18 years old is a huge landmark, although there's nothing that really comes with turning the age. You're "of age," but really what's the best part of that? There's really only two "benefits" -- either you can legally buy cigarettes, to quicken the pace of lung cancer, or walk into the "Adult" section of that creepy movie rental place your family stopped going to years ago.

Of course, turning 18 years old does bring the benefits of being able to vote, or enlist in the military.

But the fact of the matter is that most 18-year-olds don't vote, and I'm not sure the prospect of signing up to go to Iraq appeals to a lot of people.

Of course all of that leads to the really big day -- the day you turn 21.

Now you can get into all the bars your friends have been bragging about.

You can go buy a six-pack and leave that fake ID at home.

That's about it though.

Really, 21 is all about drinking, and finally doing it legally.

And really from that point on, your age becomes less and less of a defining aspect of your life.

You're not going to hear anyone getting excited about turning 25 and yelling, "I can't wait to go rent a car!"

No, each year from 21 on is more or less the same. And from time to time you'll have to subtract the year you were born from the current year to remember just how old you are.

Eventually the big 3-0 will start to creep up and then the countdown to that nightmare begins.

After 21, aside from the car rental aspect, there are no "rights" you gain from turning a year older, like the ones you got when you turned 16, 18 and 21.

Sure, there will be the big birthdays that end in zero -- 30, 40, 50, etc. -- but it definitely seems that most people don't like to be reminded those ages are approaching.

I guess for a lot of people, at some point, getting older stops being the fun thing it was at 21 and starts to remind you of your mortality.

As you continue to go through life, milestones will occur, but it seems that from the age of 21 on, you stop relating those milestones to how old you were when they occurred.

That is until you get ready for retirement or want to start taking advantage of that senior citizen discount at Denny's.