Almost everyone past the age of about thirty has said some version of the same sentence. The years are going faster. A summer that once felt endless now closes in a few weekends. Christmas seems to arrive before the last one has been put away.
The feeling is consistent enough that it has been studied for a long time, and the surveys do find it. In a 2005 study, the psychologists Marc Wittmann and Sandra Lenhoff asked 499 people aged between 14 and 94 how quickly time seemed to be moving. The interesting result was where the effect showed up. For short stretches, a week or a month, age made little difference. It was when people looked back over the past decade that the older respondents reported it had passed faster.
That detail is worth holding onto, because it tells you what kind of thing this is. The acceleration is not really about whether a given afternoon drags. It is a retrospective effect. It is about how a long stretch of the past feels when you turn around and look at it.
The explanation that is too neat
The oldest explanation is also the most quoted. The 19th-century French philosopher Paul Janet proposed that each year feels shorter because it is a smaller fraction of the life you have already lived. A year is a tenth of a ten-year-old’s life and a fortieth of a forty-year-old’s, so it should feel proportionally smaller.
It is a tidy idea, and it has survived for over a century mostly because it is easy to picture. But it does not hold up well as a main cause. The proportion changes smoothly and gradually, year by year, while the felt experience does not. People do not report time accelerating in even, fractional steps. They report decades that collapse and patches of life that resist collapsing. A purely arithmetic account cannot explain why some years stay vivid and others vanish.
The memory account
The more substantial explanation moves the question from how long you have lived to how much of a period you can later remember.
The brain does not record experience evenly. It encodes what is new, surprising or significant, and largely lets the familiar pass through unmarked. A first job, a first time in an unfamiliar city, the early stretch of a relationship: these generate a dense cluster of distinct memories. Routine does not. A commute taken five hundred times is not stored five hundred times. It is stored, roughly, once.
This is where the idea of a temporal landmark comes in. The psychologist William Friedman has shown that people locate past events in time by anchoring them to memorable reference points rather than by reading off an internal clock. You do not recall that something happened in a particular month; you recall that it happened around the move, or just before the new job, or the weekend of the storm. Memorable disruptions become the pegs the rest of the past hangs on.
A period rich in those pegs feels substantial in hindsight. A period without them has nothing for memory to catch on, and looking back, it reads as a single undifferentiated stretch. The science writer Claudia Hammond gave the everyday version of this a name, the holiday paradox: a week away, full of unfamiliar things, feels short while you are living it but long when you look back, because it left behind so much to remember. An ordinary week at home does the opposite.
Run that across decades. The years of early adulthood are crowded with firsts and therefore with landmarks. The middle decades, settled into stable work, stable home, stable routine, produce far fewer. The headline’s framing, that the acceleration is shaped by a thinning supply of those small disruptions, belongs to this account, and it is a credible one.
Why this is not settled
It is also not the whole story, and this is the part that the popular version tends to skip.
If the memory account were straightforwardly correct, the speed of a remembered decade should track the number of memories laid down in it. More landmarks, slower-feeling decade. Yet more recent research has tested that link directly and not found it. At least one study examining why the last ten years feel faster with age reported no relationship between that feeling and the number of autobiographical memories people could produce. The participants were not short of memories. The decade still felt fast. The study’s authors pointed instead toward the gradual changes in cognitive processing that come with age as the more likely driver.
The neuroscience adds its own complication. A 2025 reanalysis of brain-imaging data from the Cambridge Centre for Ageing and Neuroscience project, covering 577 people aged 18 to 88, looked at how often the brain shifts between distinct activity states while watching the same film clip. Older brains shifted between states less often. That sounds like direct support for the fewer-events idea. But the same analysis found that the brain’s recognition of major event boundaries, the significant transitions in what it was watching, stayed largely stable across the lifespan. What declined was the finer-grained parsing, not the coarse one.
So the honest position is that the felt phenomenon is well documented and reliably replicated, while the mechanism behind it is genuinely contested. The temporal-landmark account is a leading explanation. It is not a closed case, and the evidence does not all point the same way.
What to do with the advice that follows from it
The memory account tends to arrive with a prescription attached. Break your routine. Travel. Take a different road home. Fill the calendar with novelty, and you will lay down more landmarks and slow the felt passage of your life.
Some of that is reasonable. Varied, engaging experience is worth having for its own sake, and a life with more texture in it is, on most accounts, a better life than one without. If breaking routine adds something you value, that is reason enough to do it.
But it is worth being clear about what the research can and cannot promise. The claim that novelty reliably slows your retrospective sense of time is a hypothesis under active dispute, not an established result. The recent finding that memory count and the decade effect are unlinked should make anyone cautious about treating the prescription as proven. There is also something slightly self-defeating in the project of scheduling spontaneity, of treating a weekend away as a deposit into a time-perception account. A disruption pursued mainly to be memorable is already half-routine.
What survives all the caveats is modest and probably useful. Stretches of life that contained more distinct, rememberable experience tend to feel more substantial when you look back at them. Whether that is because of landmarks, or cognitive change, or some combination still being worked out, the practical reading is the same: a life with more variety in it leaves more behind.
The thing the surveys keep returning to is that the acceleration is something you notice in retrospect, never in the moment. No one feels a year going fast while they are inside it. The speed only appears when you turn around. Which means the sensation is not really a report on time at all. It is a report on how much of a particular stretch was worth keeping.
