Almost everyone over thirty has had the same disorienting thought. The year is ending again. The summer is gone. The decade just turned over and somehow nothing about the calendar feels like it lines up with how much actually happened. Time, the inner monologue insists, is moving faster than it used to.
The unsettling part is that this is not just a feeling. Neuroscientists and behavioural researchers have spent the last two decades pulling apart why subjective time accelerates with age, and the answer is more mechanical than mystical. It is not that the brain is failing. It is that the brain is not being given enough to do.
The concept of temporal landmarks
The phrase “temporal landmark” entered the research literature through a 2014 paper by Hengchen Dai, Katherine Milkman, and Jason Riis, published in Management Science. They defined a temporal landmark as any distinct event that stands out in the ordinary humdrum of life, and they showed that these moments do something specific to how we relate to time. Google searches for the word “diet” jumped 14.4% at the start of a new week, 3.7% at the start of a new month, and 82.1% at the start of a new year. Gym attendance and goal-setting followed similar patterns.
The original use of the term was about motivation, the so-called “fresh start effect” that gives the new year its hold on the human imagination. But subsequent work, including a 2018 review by Dai and colleagues in Current Opinion in Psychology, expanded the idea. Temporal landmarks are now understood as the cognitive scaffolding that lets us perceive time as structured rather than continuous. They are the dividing lines between mental chapters. Without them, the chapters bleed into each other, and a year of life starts to compress into something that feels closer to a season.
What the brain does at an event boundary
The deeper neuroscience underneath this comes from Jeffrey Zacks at Washington University in St. Louis. His Event Segmentation Theory, published in Current Directions in Psychological Science, proposes that the human brain does not perceive experience as a continuous stream. It chops experience into discrete events, marked by what researchers call event boundaries. An event boundary might be something physical, such as walking into a new room, or something conceptual, such as a goal changing or a conversation ending.
The critical finding from Zacks and his collaborators is that these boundaries are not just perceptual conveniences. They are the moments at which the brain commits experience to long-term memory. In a 2017 study published in Cognitive Research, participants who were better at identifying event boundaries when watching everyday activities also had measurably better recall of those activities afterward. The boundaries themselves were remembered more vividly than the middles. Memory, in other words, clusters around transitions.
This has a counterintuitive consequence. A week in which every day is the same week generates very few event boundaries. The brain has nothing to anchor memory to, so very little of the week is encoded as distinct. Looking back on it, the entire week feels like a single forgettable smear. Multiply that effect across years of similar routines and the subjective acceleration of time begins to make sense.
What the latest aging research adds
In September 2025, a team analysing data from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) project published findings in Communications Biology that gave Zacks’s theory a developmental dimension. Using fMRI data from 577 participants between the ages of 18 and 88, they tracked how often the brain transitions between stable neural states while watching an eight-minute Alfred Hitchcock clip.
The result was clean. Younger brains flipped between neural states more often. Older brains lingered longer in each state. Visual and prefrontal regions, the parts most involved in perception and memory, showed the steepest age-related slowdown in transitions. The researchers attributed this to a phenomenon called age-related neural dedifferentiation, in which the activity patterns of different brain regions become less distinct from one another as we age.
Translated out of the lab: as the brain ages, it parses experience into fewer mental events per unit of time. Fewer events per unit of time means fewer landmarks in memory. Fewer landmarks in memory means a year, viewed in retrospect, contains less to hold onto, and therefore feels faster.
The proportional theory and why it is incomplete
There is a popular folk explanation that has been around for over a century, often attributed to French philosopher Paul Janet. The idea is purely mathematical. When you are five, one year is twenty percent of your existence. When you are fifty, it is two percent. The brain measures change against prior experience, so each year shrinks relative to the ones before it.
This explanation has intuitive appeal but does not fit the data well on its own. A 2025 study summarised in Psychology Today tested the related hypothesis that older adults simply remember fewer autobiographical events from recent decades, and found that the data did not support it. Older adults remember meaningful experiences just as richly, sometimes more so. What changes is the rate at which new information is taken in and encoded as distinct.
The current scientific consensus is that subjective acceleration is a multifactor phenomenon. The proportional explanation may play a small role. The bigger contributors are reduced novelty, reduced neural state transitions, and the steady creep of automaticity. Adult life involves more routine, more autopilot, more days that resemble other days. The brain, having seen this kind of day before, files it under “no update required” and moves on. The day passes. Almost nothing of it survives.
How to manufacture landmarks on purpose
The practical implication of this research is that the rate at which time appears to pass is partially under volitional control. Not the actual passage of time, obviously. But the subjective experience of it can be stretched by deliberately introducing the kinds of events the brain treats as boundaries.
A few patterns emerge from the literature. Travel works because it is event-boundary-dense by design. Every new street, new meal, and new language barrier is something the brain has to encode rather than skim. Learning a new skill works for the same reason; the cognitive effort of acquiring competence at something unfamiliar generates dense neural processing that registers as “things that happened.” Even smaller interventions help. Taking a different route home. Eating a meal somewhere other than the usual spot. Calling someone you have not spoken to in months.
The mechanism is not that any of these activities is intrinsically meaningful. It is that each one creates a moment the brain has to attend to instead of pattern-match. Attention, in event segmentation terms, is what produces a boundary. And boundaries are what produce the felt sense of time having happened.
The takeaway
The unsettling acceleration of time is real, but it is not a sign of cognitive decline in any meaningful sense, and it is not inevitable in the way it often feels. What it tracks, mostly, is the slow accumulation of routine and the corresponding decline in events the brain finds worth marking.
The research, taken together, suggests something almost optimistic. People who feel time slipping away faster every year are not losing anything intrinsic to them. They have simply stopped feeding the system that creates the felt experience of duration. The fix is unglamorous. It looks like a slightly different Tuesday. A new route. A real conversation. A weekend that does not resemble the last one. None of it requires a dramatic life change. It just requires giving the brain something it has not seen before, and then doing it again next week.
