You've said it. Everyone over thirty has said it. At the end of December, at a birthday, on a Sunday evening that arrived before the weekend seemed to start: where did the time go?
It's not a figure of speech. It's a description of something real — a shift in the texture of experienced time that nearly every adult recognises and nobody can quite explain. The summers of childhood lasted forever. An afternoon could contain a lifetime. A single school year held enough experience to fill what now passes in a month.
And then, at some point — gradually, then all at once — time began to accelerate. The years started collapsing into each other. Seasons blurred. You looked up from your work and a decade had passed, and the decade felt like the length of a single childhood summer.
This is usually filed under "getting older" — a vague, slightly melancholy observation that everyone makes and nobody examines. But in 2025, a team of neuroscientists at the University of Birmingham and Radboud University in the Netherlands looked at it directly. And what they found was precise enough to change how you think about the rest of your life.
What the study measured
Selma Lugtmeijer and her colleagues analysed fMRI brain scans from 577 participants, aged 18 to 88, drawn from the Cambridge Centre for Ageing and Neuroscience cohort. During the scans, each participant watched the same eight-minute film clip — an episode of Alfred Hitchcock Presents called "Bang! You're Dead."
The researchers weren't interested in what the participants thought of the film. They were interested in how the brain segmented the experience. Using a data-driven method, they tracked what they called "neural states" — stable patterns of brain activity that persist for a period and then shift to a new pattern. Each shift represents the brain registering that something has changed — a new event, a new scene, a new moment worth encoding.
The findings, published in Communications Biology, were clean. Younger brains flipped between neural states more frequently. Older brains lingered longer in each state. The regions most affected were the visual cortex and the ventromedial prefrontal cortex — the areas most involved in perception and memory.
In plain language: the older you get, the fewer "cuts" your brain makes in the continuous film of your experience. The movie of your life isn't getting shorter. It has fewer frames.
The researchers called this "neural temporal dedifferentiation." The brain's specialised responses — its ability to distinguish between one moment and the next, between one face and another, between one scene and the next — become less distinct with age. The editing slows down. The scenes run together. And when you look back at a year and feel like it passed in a blur, that feeling has a neural correlate: fewer distinct moments were encoded. There is, quite literally, less to remember.
Why the obvious answer isn't enough
The most popular explanation for time acceleration is mathematical. A year at age five represents 20% of your entire life. A year at fifty represents 2%. Each year is a shrinking fraction of the total, and the shrinking fraction is why it feels shorter.
This is true, and it's tidy, and it explains the general trend. But it doesn't explain the exceptions — and the exceptions are where the interesting question lives.
Think of a week you spent in a new country. A place you'd never been, where the food was unfamiliar and the streets were confusing and every small task required attention. That week, in retrospect, probably felt long. Rich. Dense with experience. Maybe it felt longer than the entire month that preceded it — a month spent in your routine, at your desk, doing what you always do.
The proportional theory can't account for this. The week and the month are the same fractions of your life. But one feels expansive and the other feels like it barely existed. Something other than proportion is at work.
The Radboud study points at what that something is: temporal landmarks. The brain encodes experience by marking moments of change — moments when the input is novel enough to warrant a distinct neural state. A new restaurant, an unfamiliar street, a conversation that surprised you, the first time you did anything. These aren't dramatic events. They're novelty. New input the brain hasn't automated.
And they're what time is made of, subjectively.
A week with ten landmarks feels long in retrospect, because there are ten distinct moments to remember. A week with none feels like it never happened, because nothing was marked. The brain didn't bother encoding something it had seen a thousand times before. It let the week pass without making a note.
The efficiency trap
This is where the finding becomes uncomfortable, because it implicates something most adults consider a virtue: routine.
The brain is an efficiency machine. It automates what it can. The drive to work, the morning coffee, the weekly meeting, the evening scroll — each repetition makes the pattern smoother and requires less conscious processing. This is genuinely useful. It frees cognitive resources for higher-level thinking. It makes the day manageable. It lets you function without treating every moment as new.
But automated experience doesn't get encoded as distinct memory. The brain doesn't mark what it's already modelled. The thousandth drive to work is neurologically invisible — it happened, but it left no landmark. The result is that the more optimised your life, the fewer landmarks you create. And the fewer landmarks, the faster time feels.
There is a quiet irony here. The life you built for stability — the settled routine, the familiar rhythms, the predictable weeks — is the life that disappears fastest in retrospect. Not because you weren't living it. Because the brain, having automated it, stopped recording it.
You traded novelty for comfort. The comfort is real. The cost is experienced time.
What children have
Children don't have longer days than adults. The clock runs at the same speed. What they have is an environment saturated with novelty.
A five-year-old's Tuesday contains dozens of things they've never seen, tasted, touched, or figured out before. The texture of a leaf. The way water behaves in a cup. The rules of a game they just learned. A word they haven't heard before. Every one of these is a temporal landmark — a moment the brain registers as distinct and encodes accordingly.
By the end of the day, the child has accumulated a dense record of distinct moments. When they look back — not that children do much retrospective assessment — the day feels enormous. Because it was. Not in minutes. In moments.
An adult's Tuesday, by contrast, may contain zero landmarks. The same commute, the same desk, the same lunch, the same screens, the same conversations about the same topics. The brain has automated all of it. Nothing requires fresh encoding. The day passes and leaves almost no mark. By Wednesday, Tuesday is already gone — not forgotten, exactly, but never properly recorded.
This is what the Radboud study is measuring at the neural level. The child's brain flips between states rapidly — every new input triggers a shift. The older brain lingers in each state, because the input isn't new enough to trigger a transition. The editing pace has slowed. The days have fewer frames.
Presence as time-creation
This is where the contemplative angle earns its place, because what the traditions describe as "presence" maps directly onto what the neuroscience is measuring as "temporal landmark creation."
When you are fully present — attending to this moment without planning the next one, without replaying the last one, without running on autopilot — the brain is processing input as novel. Even a familiar room becomes new when seen with fresh attention. The routinised gaze slides over it — the brain has already modelled the room and doesn't bother updating the model. The present gaze meets it as though for the first time, and the brain encodes the encounter.
This is why retreat experiences feel long despite being short. Why a week of travel feels like a month. Why a single conversation that genuinely surprised you can stretch an evening into something you remember years later. Presence is the brain's landmark generator. Each moment of genuine attention creates a frame the brain bothers to keep.
Without presence, time collapses into undifferentiated blur. The weeks run together. The months vanish. The years, looked back on, contain almost nothing — not because nothing happened, but because nothing was attended to with enough freshness to be marked.
Linda Geerligs, a co-author of the Radboud study, offered a practical observation in an interview: "Learning new things, travelling, and engaging in novel activities may help make time feel more expansive in retrospect." She added: "Maybe even more important, though, are meaningful social interactions and activities that bring joy."
The neuroscientist and the meditator are pointing at the same thing from different directions. One says: create temporal landmarks. The other says: be present. The instruction is the same.
What you're actually running out of
The fear of ageing is usually framed as running out of years. The research suggests something more precise.
You're not running out of time. You're running out of moments.
Not because fewer remain — though of course they do — but because fewer are being created. An 80-year-old who lived in unbroken routine may have experienced subjectively less life than a 60-year-old who maintained sustained attention and novelty. The clock gave them both the same quantity of time. The brain gave them vastly different densities.
This is not a call to "live every day like it's your last" — that's a bumper sticker, not a practice, and the anxiety it produces probably collapses more time than it creates. The observation is quieter and more specific: the quality of your attention determines how much life you experience. Not how much happens to you. How much registers.
The same Tuesday can contain a lifetime or nothing, depending on whether anyone was there when it happened. The same year can feel expansive or evaporated, depending on how many moments were met with enough presence to be recorded.
What time is made of
There's a version of this observation that sounds like advice, and a version that sounds like something closer to the truth.
The advice version says: do new things, travel, break your routine. And that works — novelty does create landmarks, and landmarks do make time feel longer. It's good advice, as far as it goes.
The deeper version says something different. It says that time, as you experience it, is not a quantity that passes. It's a quality that is created — moment by moment, landmark by landmark, by the act of attending to what's here.
The contemplative traditions didn't talk about time perception or neural states. They talked about presence. About the difference between a life lived on autopilot and a life lived with attention. About the possibility that a single moment, fully met, contains more than a decade of distraction.
They weren't being poetic. They were being precise. And the neuroscience, two and a half thousand years later, is arriving at the same coordinates: the present moment is the only one the brain bothers to record. Everything else — the plans, the routines, the automated days — passes through without leaving a mark.
Your life isn't getting shorter because you're running out of years. It's getting shorter because the moments are passing through you unrecorded — each one a frame the brain didn't bother to keep, a landmark that was never made, a second of experience that will not be there when you look back.
The years are the same length they've always been. What's changed is whether you were there for them.
Sources and further reading:
- Lugtmeijer et al., "Temporal dedifferentiation of neural states with age during naturalistic viewing," Communications Biology (2025) — on neural state lengthening with age and reduced temporal landmark creation
- Adrian Bejan, "Why the Days Seem Shorter as We Get Older," European Review (2019) — on neural processing speed and mental image generation declining with age
- Geerligs & Campbell, co-authors of the Lugtmeijer study — on novelty, meaningful connections, and time expansion in retrospect
- Enric Espel Sanchez, "Time in a Bottle: A Psychophysics Study of Human Time Perception Through Aging," University of Helsinki preprint (2024) — on the mathematical framework for time perception changes across the lifespan