Well, now my age has a 2 as the first digit... gosh it's been quite a long time now...
21st will be something interesting to look to, since that's when I'm completely in the eye of the law, considered an adult, and thus there's no more age restrictions for a long time before I fail to meet the maximum age limit for certain activities lol. More importantly though, it'll be the beginning of my first vacation to a foreign land without supervision of any sort throughout the trip, and not visiting someone who lives there. I.e. A greater degree of freedom.
I'm grateful to have not spent (and will not) any birthdays in green, or doing army related stuff. I have (and will) only pass through 1 birthday in the army, thanks to my service dates. And thankfully, we were granted a day off yesterday, so all's well!
Somehow, for us younger people, each year we pass (and each birthday we celebrate) means alot to us. Every year we experience something almost totally unlike the previous year. There's so much change within the first 3 decades of our lives, that each birthday carries with it much meaning. After which, most tend to fall into a repeated pattern, a routine that carries them on throughout the next few decades and they just let life pass them by. I'd hate to get into that, because then the years seem very fast, and before you know it, you're getting old, old enough to start having physical problems, mental problems, etc. I hereby resolve to never let this happen. (actually it's probably subconsciously resolved a few years ago already, I'm just declaring it right now) I'll live my life to the fullest, treasuring each day each moment, good or bad, because I only have so many years.
20 is really small if you want to look at our universe. By the time we're dead, information from our birth has not even made it 10% across our Orion Arm of our Galaxy, let alone exit the Arm or the galaxy. The nearest neighbouring galaxy, Andromeda, is 2.5 x 106 light years away. There, information of the modern human existance isn't even known yet. We've only existed for around 2 x 106 years. Really young... The sun would not have changed much either by the time an individual's life is through. We're really young on the galactic scale... (some hope there! haha)