As a kid I held a kind of sacramental reverence for the first time I wrote the date of the new year. Like most children, I never wrote a date like MM/DD/YY for any other reason than to mark the top of my homework. In school, the date was linked to TODAY.
Whereas the days and months changed consistently, the year was locked in what seemed like forever. Toward the end of the year I would remind myself that I had once written the year before at the top of my paper, and even though I knew it was true, I didn't believe it. It had been this year for so long that the ones before had never existed. I would imagine going to heaven and God telling us all that he had programmed the past in our minds, that the only year that ever really existed was 1989.
At 12:01 on January 1st, 1990, I stood under the front porch in awe that I had lived an entire decade, that it was a new decade, that the 80s were gone and that I would never again write "mm/dd/89" at the top of my paper. When I wrote the "90" on the far right of the dashes for the first time, I almost felt like I had done something wrong.
Many people I know subscribe to the theory that we experience time as a percentage of the time we have lived. Thus, one day to a child is much longer than a day to a 94 year old man because the old man has lived longer. Although time does pass more quickly now that it did when I was a kid, I think our experience of time passing has much more to do with whether or not we are waiting for something to happen in the future and the length of our attention spans (which is tied to our ability to distract ourselves). For me, childhood was just biding time until I could have all the privileges that came with adulthood. I wasn't very good at distracting myself either. Now, when I can't wait for something to happen in the future, such as drinking the French champagne I bought for tonight, I am able to distract myself and the wait doesn't seem so long.
However, the sancitity of writing the new date has changed. It's not that things diminish with time. It's not that I've lived so many years (which I haven't) that one more is insignificant. I'm not so busy that I can't be bothered with petty things. The special feeling of writing the new year's date has been corrupted by credit card expiration dates.
Yes, I have already written or typed 01/2007 hundreds of times. My next payment on my student loan has been due 09/01/07 for forever. I've already mentally journeyed to 10/15/07 every time I consider my car insurance premium. Thus, it's not that being an adult diminishes the passing of time, it's that our contemplation of future dates is almost always embedded in when our bills are due.