After about age 25 many culturally important events — finishing education, establishing a career, marrying, having children — tend to cluster. These milestones create a denser sequence of noteworthy changes, so fewer days feel novel and more are experienced as steps toward long-term goals. At the same time people grow more aware of biological aging and life’s finitude: heightened awareness of limited time makes remaining years feel scarcer and attention more future-oriented. Together, denser milestone clustering and increased awareness of mortality reduce novelty and amplify goal-focused attention, causing subjective time to feel faster.

References: research on subjective time and novelty (e.g., Flaherty, 1999; Friedman, 1993) and cultural studies on life-course milestones (e.g., Elder, 1998).

As you age, each additional year represents a smaller fraction of your total life. At 10, one year is 10% of your life; at 40, it’s only 2.5%. Because our sense of duration is often relative rather than absolute, smaller fractional increments feel subjectively shorter. Psychophysics (e.g., Weber–Fechner principles) shows that perceived change depends on proportional differences: equal absolute intervals are judged shorter when they comprise a smaller share of prior experience. Thus, after 25, years can feel like they pass more quickly simply because each year makes up a smaller slice of the life you already have.

Relevant concept: Weber–Fechner law on perceived magnitude (see basic psychophysics literature).

As we age, our subjective sense of how quickly time passes is influenced by the number of distinct, memorable events we form—what cognitive scientists call “memory density.” Younger people typically experience many novel situations (firsts, big changes, intense learning), which create richly encoded episodic memories. When you later look back, a year packed with such distinct memories feels long because it contains many retrievable episodes.

After about the mid-20s, life often becomes more routine: fewer novel milestones and fewer highly salient episodic memories are formed. With lower memory density, retrospective judgments compress those years—there are fewer marker-events to “fill” time—so they feel shorter. Daniel Kahneman’s work on retrospective duration and Endel Tulving’s research on episodic memory explain how the quantity and distinctiveness of memories shape our perception of elapsed time.

As we age past our mid‑20s, several biological and physiological changes can alter how we experience time. Metabolic rate and circadian rhythms shift with age, affecting arousal and the internal “clock” that helps segment moments—slower metabolism and flatter circadian amplitude can make intervals feel shorter. At the neural level, reduced plasticity and declines in dopaminergic function (dopamine is important for timing and reward prediction) change temporal processing: lower dopamine is associated with an underestimation of durations and fewer distinctive memory markers for events. Together, these changes reduce the number of salient temporal cues and slow internal pacing, producing the subjective sense that life is passing more quickly.

References: research in neuropsychology on dopamine and time perception (e.g., Meck, 1996; Buhusi & Meck, 2005) and studies of aging, circadian change, and temporal processing (e.g., Wearden, 2005; Monk, 2005).

• Proportional perception: At 10, one year is 10% of your life; at 40 it’s 2.5%. Example: a summer holiday felt endless at 12 but a similar break at 35 seems to vanish.

• Predictability and routine: Repetitive weeks blur together. Example: when your weekdays are always commute–work–dinner, months look the same; taking a new evening class breaks the loop and makes time feel fuller.

• Memory density: Distinct events make time seem longer in retrospect. Example: your first year at university (many “firsts”) seems longer than a later year with fewer milestones.

• Attention and cognitive load: Divided attention reduces moment-to-moment awareness. Example: juggling work emails, bills, and childcare means you notice fewer details of the day, so weeks pass quickly.

• Biological factors: Changes in neural processing affect timing. Example: people report fewer intense emotional highs or novel dopamine-driven experiences with age, which can shrink subjective duration.

• Social framing: Milestones cluster and awareness of aging increases urgency. Example: turning 30 prompts reflections and comparisons that make prior years feel like they flew by.

Tip: To slow subjective time, introduce novelty (travel, learning), practice mindfulness, and create intentional rituals that produce memorable moments.

Selected references: Ornstein, R. (1969). The Psychology of Time; Kahneman, D. (2011). Thinking, Fast and Slow; Wittmann, M. (2013). The inner experience of time.

Daniel Kahneman’s Thinking, Fast and Slow links our subjective sense of time passing to how memory encodes events. Two key ideas explain why life feels faster after about 25:

• Novelty and encoding density. When we are young we experience many new, attention-demanding events; these create rich, distinct memory traces. A period filled with novel experiences later reconstructs as long and dense in memory. As routines replace novelty with age, fewer distinct memories are formed per unit of time, so retrospective judgments report shorter durations.

• Retrospective versus prospective time. Kahneman distinguishes memory-based (retrospective) judgments from on-the-spot (prospective) time awareness. The “speeding up” is mainly retrospective: looking back, we perceive earlier years as longer because more memorable events occurred then. In the present moment (prospective), time can still feel slow when attention is heightened.

Put simply: fewer novel memories per year → less remembered content → reconstructed sense that earlier years were longer and recent years pass more quickly. (See Kahneman 2011, ch. 46 on memory and duration.)

Ornstein (1969) argues that our experience of time depends on how many novel events or “time markers” we encode. When we are young, we encounter many new situations, so more distinct memories are laid down per unit of clock time; retrospection therefore stretches subjective duration. After about 25, life often becomes more routine: fewer novel events are encoded, so the same amount of clock time contains fewer memorable markers and thus feels shorter. Ornstein also discusses attentional and emotional factors—when attention is absorbed, time seems to pass quickly in the moment but leaves fewer retrospective cues. Physiological and information-processing changes (e.g., shifts in arousal and processing speed) further influence time judgments. Overall, decreased novelty and altered cognitive encoding explain why decades after 25 can subjectively “speed up.”

Reference: Ornstein, R. (1969). The Psychology of Time. New York: Harper & Row.

Wittmann (2013) investigates how subjective time — our inner sense of how fast or slow time passes — is constructed in the brain and why it changes across the lifespan. Key points relevant to the common report that life “speeds up” after mid-twenties:

• Multiple time mechanisms: Wittmann distinguishes different neural and cognitive systems for timing (milliseconds to seconds vs. minutes to hours vs. months and years). Short-interval timing relies on physiological pacemakers and attention; long-term temporal experience depends on memory, event segmentation, and life narratives.

• Role of attention and change: When we attend closely to events, time feels slower; routine or unvaried sequences lead to fewer encoded events and a feeling that time passed quickly. After 25 many people settle into repetitive patterns (work, habits), producing fewer distinctive memory markers and thus a compressed retrospective sense of time.

• Memory and event density: The perceived duration of past periods depends on the number and vividness of stored events. Younger years often contain novel, formative experiences (education, travel, identity changes) so they seem longer in retrospect. As novelty declines with age, retrospective time seems shorter, producing the impression that life accelerates.

• Emotional and physiological factors: Age-related changes in affect, arousal, and dopaminergic function influence time perception. Reduced novelty-seeking and altered arousal can modify internal timing mechanisms and the subjective flow of time.

• Subjective vs. objective time: Wittmann emphasizes that inner time is an experience constructed by brain processes (attention, memory, interoception) and need not track clock time. The “speeding up” feeling is a psychological effect of how experiences are encoded and recalled, not a change in physical time.

In short: Wittmann’s account explains the post-25 acceleration as emerging from reduced event density and novelty, altered attention and memory encoding, and neurophysiological changes that together compress retrospective duration and make life feel as if it’s passing more quickly.

Reference: Wittmann, M. (2013). The inner experience of time. Philosophical Transactions of the Royal Society B: Biological Sciences, 368(1628), 20130066.

As people enter adulthood they typically adopt more repetitive schedules—commuting, fixed work hours, household tasks, caregiving—so days and weeks contain fewer truly novel events. Cognitive and experimental psychology show that subjective time is tied to how much new information we encode: novel experiences require more attention and create richer memory traces, which expand perceived duration; by contrast, routine produces fewer distinct memories and compresses subjective time. In short, fewer new experiences = less encoded detail = the feeling that time is passing faster (see research on temporal perception and novelty effects; e.g., Fraisse 1984; Zakay & Block 1997).

As people take on more responsibilities in adulthood—work, family, finances—their attention becomes divided and cognitive load rises. When attention is spread thin, fewer novel details of everyday experience are encoded into memory. Since subjective duration is strongly tied to the number and richness of stored memories, periods with less moment-to-moment attention seem to pass more quickly in retrospect.

Mindfulness and focused attention counteract this effect: paying close attention to present-moment experience increases encoding of detail and novelty, producing a denser set of memories and thus a slower-feeling passage of time. Practically, cultivating mindful practices or deliberately creating new experiences can make time feel fuller and less accelerated.

(See: William James on the psychology of time perception; contemporary work on attention, memory, and subjective duration—e.g., Zakay & Block, 1997; Arstila, 2012.)