They say time flies when you’re having fun.

Apparently it flies even when you’re not, especially after you reach a certain age.I’m not sure exactly what the cutoff for that age is, but I’m pretty sure I’ve reached it.Here’s an example: the adorable Mary Engelbreit calendar hanging in my kitchen proclaims that it’s December. No surprise there, unless you look a little closer. It’s last year’s calendar. Yep. My calendar says it’s 2014.Now if I could actually get that whole stopping time thing to work, or at least if I could slow time down a bit, I would be a millionaire.I have a brand-new 2015 calendar upstairs in my home office, still in the sleeve; just waiting for me to fill in all the birthdays, anniversaries and other important dates.Hardly seems worth the effort at this point.I’d like to say that despite not having a current calendar to peruse, I never missed a birthday this year, but that would be a lie. I’d also like to say that I’d mailed all the cards I bought for the birthdays I did remember, but that, too, would be a lie.My intentions are good. I really do mean to send out those cards, letters or thank you notes, but I get busy with something else, and just tell myself I’ll do it tomorrow. Before I know it, tomorrow was a few weeks ago, then a few months, and here we are — a year later.While my issues with procrastination are one thing, the fact remains that once we get past a certain age, like maybe our 20s, time seems to move faster. When we get a bit older (let’s just assume I’m no longer in my 20s or 30s), time begins to move at breakneck speed.When I was a teenager, I couldn’t wait until I turned 17 so I could get my license. Everyone else wanted to be old enough to drink. I just wanted to drive. It took decades for me to finally hit that magic number, and I can remember going for my driver’s test like it was yesterday (OK. Two yesterdays. I failed the first time, but it really wasn’t my fault).I’ve done a lot in the years since I got my license. Regardless, it still seems like it wasn’t all that long ago.A lot of people feel the same way that I do: that time flies.Apparently, there’s an explanation for that. It may not make it any easier to accept, but it does make it more understandable.All the way back in 1890 (now that was a long time ago), psychologist William James was of the opinion that it seemed time was flying for us once we became adults because we no longer experienced the firsts that bracketed our younger days, and fewer memorable events, like the first day of school or our first kiss.Another theory, proclaimed even earlier, rationalizes that the way one perceives the passage of time is relative to that person’s age. To a 1-year-old, a year is 100 percent of their life, while to someone who is 50, a year may be only 2 percent of their life, providing they live to a ripe old age.That makes sense, but it doesn’t make it any easier to swallow. In the meantime, the list of things I’ve yet to do keeps getting longer.And a fancy new wall calendar for 2016? I’m not even going to bother. It will be December again before we know it.