My aunt recently passed away after a long, grueling battle with cancer. An incredibly decent woman, she spent her final years insisting that time is our only non-renewable asset and that the hands on the clock move faster every year you stay alive.

When I was younger, I dismissed this as little more than garden-variety elder sentimentality. Standing at her grave on a rainy Sunday morning, I finally understood what she meant.

We built the effortless paradise our ancestors could only dream of, only to discover that it can make life feel like one long weekend.

In the 19th century, a French philosopher named Paul Janet offered a mathematical explanation for the subjective acceleration of time. He argued that each passing year feels proportionally shorter for a very specific reason. To a 2-year-old child, twelve months equals 50% of all known reality. By the time a person hits 50, that same year accounts for a rather pathetic 2% of their personal timeline. Janet's arithmetic offers an elegant explanation for why the years seem to shrink, though it doesn't tell us much about what is happening inside our skulls.

Reeling in the years

A study published earlier this year offers a more complicated explanation. Researchers have long suggested that time seems to accelerate as we age because adulthood lacks the novelty of childhood and adolescence. When every day resembles the last, we have fewer distinctive memories to look back on, making entire years seem to disappear.

Researchers examined 120 adults, ranging in age from 20 to 91, and found no significant relationship between how quickly participants felt the previous decade had passed and either the number of personal memories they recalled or the importance they attached to those memories. Instead, the sensation of accelerating time was associated with poorer cognitive performance, particularly on a test of delayed memory recall.

The findings suggest that our ability to form new memories may help explain why time seems to speed up as we age. They also raise an uncomfortable question about how much of our lives we actually remember.

Wasted on the way

Consider the difference between stepping onto an airport shuttle in a strange city and making your daily commute to work. In the unfamiliar city, you notice everything: the smell of diesel, the strange angle of the streetlights, the driver's odd accent, and the dodgy-looking individual eyeing your wallet. Decades later, you may still remember that seven-minute ride.

Contrast that with your daily commute. You have driven that specific stretch of road thousands of times. The route is so familiar that you barely need to think about it. You arrive at your desk with 40 minutes missing from your conscious existence, unable to recall much of what happened between your driveway and the office.

Smartphones have given us another remarkably efficient way to make hours disappear. Tens, perhaps hundreds, of millions around the world spend their afternoons tapping on glass screens, watching short videos of strangers selling snake oil or arguing over trivial issues. The ultimate joke of the digital age involves paying hefty sums for a device that competes so relentlessly for our attention that we barely notice our own lives passing.

Even our attempts to preserve memories can interfere with forming them. In a 2014 study, psychologist Linda Henkel found that people who photographed objects during a museum tour subsequently remembered fewer details about them than people who simply observed them. The effect wasn't universal — taking more focused photographs produced different results — but the finding raises an interesting possibility. A parent filming a child's piano recital might come away with a beautiful MP4 file and surprisingly little memory of the performance itself.

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Where the time goes

Family life has its own peculiar relationship with time. Raising kids feels like an endless march through tedious chores — changing diapers, insisting that Legos not be put in one's mouth, packing lunch boxes, folding laundry, and driving to soccer practice. Yet parents, from Boston to Brisbane, are shocked by how quickly their toddlers turn into college freshmen.

Kids force constant novelty into a household through broken bones, lost teeth, spontaneous questions about death, and the unexpected introduction of garden creatures into the living area. Individual days can feel agonizingly long because every hour requires attention, yet the years somehow fly by in retrospect.

Modern society has, in many ways, made convenience the guiding principle of daily life. We tap an icon to order takeout. We stream movies dictated by predictive algorithms. We substitute memes and text messages for actual human voices. We built the effortless paradise our ancestors could only dream of, only to discover that it can make life feel like one long weekend.

And yet some of our most enduring memories come from doing the same things over and over again. Repeating specific holiday meals or annual camping trips may seem like a mindless, even pointless, routine to an outsider. It is not. Those moments become lasting markers in our memories. No one remembers a random Tuesday from six years ago, but everyone remembers the Thanksgiving when the oven exploded or the road trip when the radiator burst and Dad used some colorful language to convey his thoughts. Traditions give us memorable moments to return to as time moves on.

Now that my aunt is gone, I keep thinking about those Sundays at her house. I think of the roast dinners, the endless slices of cake, the hot tea, and her constant reminders to do something useful with my life.

At the time, I thought those Sundays would go on forever.