Two kinds of fast
Eventually a photograph turns up of a dinner you remember as fairly recent. The restaurant has since closed, the friend beside you has moved twice, and the telephone on the table possesses a home button. You estimate three or four years. The photograph says nine.
The alarming part is not that the dinner is old. It is that the intervening years appear to have left no forwarding address.
This is usually when someone explains that time speeds up as we age. Childhood summers were enormous. Our twenties had discernible chapters. Then the forties arrived carrying work, errands, medical portals and a December that began while we were still dealing with September.
A Tuesday can be interminable at 2:14 and disappear completely by Christmas.
The experience is common. The scientific explanation is not. Studies do find an association between age and the feeling that time has accelerated, but it is generally modest and appears most clearly when people judge the previous decade—not the previous week, month or year.
In one study, Marc Wittmann and Sandra Lehnhoff surveyed 499 people between fourteen and ninety-four. Age explained only a limited share of the differences among them. Another study of 1,865 adults in New Zealand and the Netherlands found that people at nearly every age described time as passing quickly. Again, the clearest age difference concerned the previous ten years.
There is no neurological switch that flips on one’s fortieth birthday, although the birthday industry would no doubt sell a tasteful commemorative version.
“Your forties go faster” describes a familiar impression, not a settled biological law. The most defensible finding is narrower: older respondents often describe the preceding decade as faster, while age differences for shorter recent intervals are weak or absent.
Part of the confusion comes from asking one word—time—to do several jobs. Psychologists distinguish prospective duration judgments, made while someone knows time is being measured, from retrospective judgments reconstructed afterward. They also study the felt passage of time: whether an interval seemed to fly or drag. These questions sound related because they all involve a clock. The mind answers them using different paperwork.
A repetitive afternoon may crawl while it is happening because attention has nowhere more interesting to go. Months later, the same afternoon may have vanished because it left few distinctive memories. A vacation can fly while lived and then occupy a large territory in memory.
The paradox is administrative: attention and memory keep separate books.
The fraction theory explains too much
The most elegant explanation is also the one people remember. In 1877, the French philosopher Paul Janet proposed that a year feels shorter because it represents a shrinking fraction of the life already lived. To a ten-year-old, a year is one tenth of existence. To a fifty-year-old, it is one fiftieth.
The theory has the beauty of a rule worked out on a cocktail napkin. It produces an immediate feeling of understanding and, with only minor encouragement, a graph alarming enough to ruin a birthday.
It does not fit the evidence particularly well. If subjective time followed Janet’s ratios, acceleration would be dramatic and mathematically predictable across ages and intervals. People do not report anything so orderly. A year at forty does not reliably feel half as long as a year at twenty, and shorter recent periods often show little relationship with age at all.
The problem is not that proportion is irrelevant. An eight-year-old has less experience against which to compare a year, and childhood is full of intervals that are large relative to the life containing them. But a year is not perceived as a slice on a pie chart. It is lived through attention and reconstructed through memory.
There is no sound basis for claims such as “one year at eighty feels like four days.” The equations often circulated online are metaphors wearing lab coats.
Emotion complicates matters further. An absorbing evening can seem brief. Anxiety, sadness, pain and boredom can alter the felt speed of a present interval. Meaningful activity may make time pass quickly, which means that “fast” cannot simply be translated as “empty.”
We have at least three unreliable clocks: the one we watch, the one we remember and the one we use to complain about our age.
Memory edits the calendar
Memory is less an archive than an aggressive compression algorithm. It does not preserve every commute, breakfast and conversation as a separate file. Familiar experiences are grouped into categories: work was busy, the usual summer, we were dealing with the house.
At twenty, a year may contain first apartments, first jobs, breakups, disasters and reinventions. An equally complicated year at forty may be filed under “work.” We may remember childhood as events and adulthood as categories.
This gives the novelty explanation much of its force. Distinctive events create potential memory boundaries and retrieval cues. Routine permits the mind to store the general arrangement rather than every repetition. Looking backward, a period with few accessible divisions may appear compressed.
Experiments support part of this account. In a series of studies, researchers prompted participants to organize the previous year into broader or narrower categories. Those encouraged to “chunk” the year more broadly tended to judge it as having passed faster.
But “make more memories” is not a complete theory, and novelty is not a scientifically validated prescription for slowing a decade. A 2026 study of 120 adults aged twenty to ninety-one found the familiar association between age and the apparent speed of the previous decade, but much of it was driven by especially slow ratings among people in their twenties. Remove that group and the simple age relationship weakened. The number and reported importance of autobiographical memories did not explain the effect.
Lower performance on a delayed-recall task was associated with faster decade judgments, suggesting that the capacity to encode new episodic information may matter. The study was small and correlational; it cannot tell us that memory decline causes accelerated years. Its larger contribution is less satisfying and more useful: the tidy answer remains untidy.
Busyness supplies another candidate. Studies have found that time pressure predicts perceptions of rapid passage more strongly than age does. Yet causation is difficult to assign. Rushed people may experience time as faster, or people may look back on a crowded year and infer that it must have flown. “The year disappeared” may be a report of perception, a summary of memory or a culturally acceptable way of announcing that one has been terribly productive.
Boredom lengthens the invoice and shortens the receipt.
Recent research complicates the melancholy interpretation too. Periods associated with growth and satisfaction are often remembered as having passed quickly. Some years disappear because nothing distinguished them. Others disappear because we were too absorbed to watch them leave.
Can a year be widened?
The usual advice is to seek novelty: travel, learn a language, take a different route, order something mysterious from the menu. These may produce distinctive memories. They may also make the experience pass more quickly while it is happening. The techniques that enlarge a period in memory can accelerate it in the present.
There is no established intervention that reliably makes an entire decade feel longer. This is probably fortunate. A reliably lengthened decade might resemble a meeting whose organizer has discovered additional slides.
A more reasonable aim is not to slow time but to reduce indiscriminate compression. Meaningful event boundaries may help: projects with visible stages, deliberate beginnings and endings, small records of what changed, and pauses long enough to notice that one period has become another.
Recording one specific development each week is not a temporal treatment, and it comes with no guarantee of a subjectively expanded year. It does, however, give memory more retrieval cues than “March was busy.” Revisiting those markers may preserve distinctions that routine would otherwise merge.
The point is not to manufacture novelty for novelty’s sake. A year can be highly differentiated by caring for someone, learning a difficult skill, recovering from illness, building a garden or completing a project whose stages require different versions of us. Meaning can divide time as effectively as spectacle.
Nor should rapid time always be treated as theft. Pleasure, concentration, companionship and growth may all pass quickly. Fast is sometimes the speed of a life being inhabited rather than observed from the clock tower.
The forties do not contain fewer minutes than the twenties. They may contain fewer firsts, more categories, greater time pressure and a memory system increasingly skilled at summarizing repeated life. But none of these explanations owns the phenomenon outright.
We cannot add time by watching it. We can only give memory more reasons not to merge the days.
The aim is not to make Wednesday drag. It is to keep March from becoming a folder marked Miscellaneous.
Exhibit record
- Wittmann and Lehnhoff, “Age Effects in Perception of Time”
- Friedman and Janssen, “Aging and the Speed of Time”
- Droit-Volet and Wearden on passage-of-time judgments
- Landau and colleagues on memory organization and life tempo
- Teghil and colleagues on memory encoding and decade-speed judgments
- Ryu and colleagues on growth, satisfaction and remembered life tempo
- Landau and Ryu’s integrative review of life-tempo judgments