I always believed time acceleration with age was simply due to a given time period (e.g. 1 year) in proportion to your total life lived (proportional theory), plus life becoming more boring as we age (routine vs. novelty). But, searching a few peer-reviewed papers on the subject reveals a broader answer:
Proportional Theory: The “Wait, Wasn’t It Just January?” Effect
Summer breaks as a kid felt like an eternity. That’s because, at 10 years old, a year is a massive 10% of your life. Fast-forward to age 60, and a year shrinks to less than 2% of your entire existence. Basically, the older you get, the more life feels like someone keeps hitting the fast-forward button.
Routine vs. Novelty: The Groundhog Day Phenomenon
As kids, life is packed with novel firsts—first bike ride, first day of school, first sexual encounter, first sexual embarrassment, etc… As adults, we fall into routines: wake up, work, eat, mate, repeat. When every day starts feeling like a rerun, our brains stop marking time as distinctly, making the weeks, months, and years blend together like one big boring TV series (such as some ultra-serious British costume drama, like Downton Abbey[*]). Novelty stimulates your memory encoding process, anchoring events more distinctly in your mind.
Cognitive Speed & Attention: The “Did I Just Blink and Lose a Decade?” Theory
Some researchers believe our brains slow down how they process time as we age. Meaning we don’t pick up on all the small details of passing moments like we used to. So while a kid can stretch out a car ride by asking “Are we there yet?” every 30 seconds, adults look up from their cellphone and realize an entire week has disappeared.
Memory Encoding & Compression: The Mental Junk Drawer theory
Our brains store memories like a cluttered closet—early ones get neatly folded and tucked away, but over time, everything just gets stuffed in wherever it fits. The more experiences we accumulate, the more our memory compresses things, making childhood seem far away and your last birthday feel like yesterday. Our brains are bad at organizing, and time feels like it’s vanishing as a result. Neural efficiency often means older memories get “compressed.”
Most researchers agree it’s a combination of these factors, along with individual differences in lifestyle, health, and personality.
So, want time to slow down? Variety is the spice of subjective time. Try new things and break routines. Find a hooker new hobby. This can help “expand” your perception of time. Or, just get in your time machine and go back a few decades.
[*] (just kidding; I like Downton Abbey)