We can learn a lot from our animals about how to accept the passage of time

I had a shock yesterday when I got a license-renewal notice from the Pima County Health Department that says my dog is 9.

Facing up to the passage of time—subtracting one date from another and admitting to the appalling difference—is hard enough when it comes to people. It's so much worse when it comes to a pet. We count on them to stay forever young.

But there is no arguing with arithmetic. Incredibly, it will be 10 years ago this August that my son—Lai Fu's original master—moved to New York City to go to school, just before the towers fell. The following year, Dave talked his way out of the dorm and into a sublet, when he adopted a half-wild yellow dog from the Manhattan ASPCA. Fu turned out to be impossibly complicating to have in the city—as Dave said, sadly, "My life wasn't busy enough, so I went and got an adolescent male husky mix with separation issues"—and at Christmas, he brought him home to Tucson. Fu howled so desperately during the baggage transfer in Chicago that he broke Dave's heart and apparently upset a number of his fellow passengers. When I picked them up at the Tucson International Airport, a woman stopped us outside the terminal to ask if that was the dog that had been screaming and to say how relieved she was to see that he wasn't hurt.

So Dave will be 29 this year, and Fu really will be 9.

Dave's still in his salad days, of course, but Fu, who's a big guy, is well into canine middle age. He shows no signs of regretting his youth. Like most canines, he appears to dwell in a smell-rich, cheerful eternal present—basking in a temporal innocence corrupted only by enthusiastic anticipation of predictable, recurrent good things (dinner, people returning home, walks, treats), and short-term dread of bad ones (packing, people leaving, going to the vet). He paddles happily through the calm waters of an eternal now, as death rushes toward him at many times the speed it flies at me: Each of Fu's passing days is roughly the equivalent of a week in my life, considered from the point of view of his lifespan. Naturally, it's possible that every day seems to him like a week, or a month, or like eternity. How would I know?

At any rate, living with dogs and cats as they've rocketed through their distressingly short time on Earth has taught me some equanimity about what's natural to youth and age. Too many people, as they get older, worry that they're not having the fun they did when they were young, and that they don't have the energy or the appetite to get out, meet new people and keep up with what's happening. This, my dogs and cats have taught me, is folly.

Friends at work, for example, regularly ask me, in that Friday-afternoon ritual common to all offices, what I've got planned for the weekend. Honestly, I'm always a little stymied as how to answer. Sleeping in until 8, walking the dog, falling asleep on freshly line-dried sheets and finally getting some soil sulfur watered into the garden—my weekend pleasures are not worth describing. Yet, they are keen.

It's because I'm no longer a puppy. I think about my dogs over the years, their relentless need to play and chew things and run around when they're young, and how much quieter they become with passing time, and I think, you know, that's just how it is. When you're a young human, you want fun and sex and dancing, and you're excited about each weekend the way a young dog is juiced about each trip to the dog park. And the future's a glorious, golden blur, and you can hardly wait.

But by the time you're stiff in the hips and thick in the middle, the main enjoyments in life are things like good food and beloved, familiar companions, nice places to lie down, plenty of sleep and the blessed absence of bad news.

The perfect day in the life of a domestic primate, like that of a domestic dog, is a day exactly like any other.