Nearly everyone reports that years pass faster as they age. The experience is consistent enough to want an explanation, and several have been proposed.
The proportional explanation
A year is a tenth of a ten-year-old’s life and a fiftieth of a fifty-year-old’s. Each unit of time is a smaller fraction of what you have experienced.
Intuitive, frequently repeated, and difficult to test. It also does not explain why a week can feel long at any age.
The novelty explanation
Better supported. Memory of a period depends on how much distinct content it contains. Childhood is dense with first experiences; adult life is largely routine.
A holiday in an unfamiliar place feels long in retrospect because it generated many distinguishable memories. A month of identical commuting compresses into almost nothing.
This explains a curious asymmetry: unfamiliar periods feel slow while happening and long in memory, while routine periods pass quickly and vanish in retrospect.
The attention explanation
How much attention you pay to time passing affects how long it feels. Boredom is time perceived slowly because you are attending to it.
What follows practically
If retrospective time depends on distinct memories, then variety extends subjective life. New places, new activities, changes in routine.
That is not a productivity technique. It is an observation that a life of identical weeks will feel short regardless of how many weeks it contains.
What is unresolved
Whether the effect is memory, attention, a change in the brain’s internal timing, or all three. The experience is well documented; the mechanism is not settled.